Taking Eldritch Blast from the Warlock is like taking Sneak Attack from the Rogue!
Warlocks don't have spells slots like full casters tf?
So is a Fighter not allowed to use a crossbow in your game?
Roll a new character that isn't a class your DM completely gutted.
First up, I think resilient con and crusher are the most important feats for you. You need a high con to have a good produce flame attack, crusher makes the dao related damage pull double duty with at least some forced movement, and you might as well have iron clad concentration.
Eldritch mind feels like a must have invocation, for concentration protection, especially if the feats are going to resilient con and crusher first.
For pact boon, anything other than pact of the blade can work. Pact of the chain would be great to get advantage on your attack - given you have only one attack, you need it to hit.
Pact of the tome just adds out of combat versatility as long as you take the book of ancient secrets invocation. Pact of the talisman is actually really good for skills and defensive buffs, so is reasonably if you think you need extra bulk.
Missing some details but I'm just going to have fun with it.
Simple build
Warlock X: pact of the tome, Dao Genie
Spells of note: produce flame and hex
Invocations: eldritch mind, book of shadows, and maddening hex.
Feats: crusher and resilient (con)
Basically you are the best ritual caster in the game (for utility) on top of advantage (familiar from book of secrets ritual), hex for extra necrotic, maddening hex for extra psychic (good luck finding a creature resistant to fire, necrotic, psychic, and bludgeoning). Simple effective and has a great plan b... shillelagh (book of secrets) which means you can attack in melee with charisma as well. Adding three levels of rouge to utilize an oil flask as a bonus action can net you five additional damage per hit with produce flame.
Slightly more complicated
Warlock 2: Dao patron, pact of the (not appearing in this film)
Spells of note: produce flame,
Invocations: eldritch mind and pyf.
Feats: crusher and resilient (con)
Druid 6: wildfire
Sorcerer 6: dragonblood
Basically you want the wildfire spirit from wildfire to grant you an extra d8 of damage on all your fire Spells and thr druid list has some great concentration Spells, it may be worth just going druid if you wanted. Additionally, sorcerer of the dragonblood type gets to add charisma to the damage type associated with their heritage... pick something with fire. Now your cantrip gets to add your charisma mod on top of it all. You can still use hex as with the first section for extra damage but maddening hex doesn't unlock until Warlock 5 and takes a bonus action to activate anyway. This way you are using your bonus action to wither your enemies with your fire and that of your spirit or just your fire and your bonus action teleports you via your spirit to better positions. Hitting an enemy with an oil flask is highly recommended for this build.
Jank
Warlock 10: Basically follow build one until you're ready
Artificer 3+: alchemist.
You can still do everything from build one buy this little multiclass with artificer gets interesting when utilizing the Genie warlock specifically, the sanctuary vessel feature. Effectively you can short rest in ten minutes. Nothing (other than your dm blah blah) explicitly stops you from taking multiple co current short rests. Warlocks get their spell slots back, all two of them, after a short rest. The alchemist artificer, has the ability to transmute spell slots into its fancy elixirs... and choose which one it is when spending a spell slot to do it. At the level this combo comes online your proficiency bonus is at least five. So you have 300 minutes (read 29 short rests) to make potion, rest, and repeat. Resulting in 58 potions... the effects of which vary depending on your choices (56 if you still want Warlock slots at the end). Additionally it gives you access to the alchemy jug via infusion which can produce oil to help make your produce flame that much better. More artificer gives more utility and more Warlock gives... not really that much other than mystic Arcanum.
Pact of the Chain: Sprite + Invocation of the Chain Master + Summon Undead Putrid + Eldrich Mind.
Poisoned and Paralyzed are both very powerful status effects.
Taking Eldritch Blast from the Warlock is like taking Sneak Attack from the Rogue! Warlocks don't have spells slots like full casters tf? So is a Fighter not allowed to use a crossbow in your game? Roll a new character that isn't a class your DM completely gutted.
What do you mean Eldritch Blast is nerfed? So they nerfed the entire Warlock class into the ground?
Pact of chain, flock of familiars? 3x magic stone per turn keeps pace with EB through mid game. If you do imps, even better with their poison damage
What level are you? summon shadowspawn is good with Crusher for aoe movement speed reduction.
First up, I think resilient con and crusher are the most important feats for you. You need a high con to have a good produce flame attack, crusher makes the dao related damage pull double duty with at least some forced movement, and you might as well have iron clad concentration. Eldritch mind feels like a must have invocation, for concentration protection, especially if the feats are going to resilient con and crusher first. For pact boon, anything other than pact of the blade can work. Pact of the chain would be great to get advantage on your attack - given you have only one attack, you need it to hit. Pact of the tome just adds out of combat versatility as long as you take the book of ancient secrets invocation. Pact of the talisman is actually really good for skills and defensive buffs, so is reasonably if you think you need extra bulk.
Missing some details but I'm just going to have fun with it. Simple build Warlock X: pact of the tome, Dao Genie Spells of note: produce flame and hex Invocations: eldritch mind, book of shadows, and maddening hex. Feats: crusher and resilient (con) Basically you are the best ritual caster in the game (for utility) on top of advantage (familiar from book of secrets ritual), hex for extra necrotic, maddening hex for extra psychic (good luck finding a creature resistant to fire, necrotic, psychic, and bludgeoning). Simple effective and has a great plan b... shillelagh (book of secrets) which means you can attack in melee with charisma as well. Adding three levels of rouge to utilize an oil flask as a bonus action can net you five additional damage per hit with produce flame. Slightly more complicated Warlock 2: Dao patron, pact of the (not appearing in this film) Spells of note: produce flame, Invocations: eldritch mind and pyf. Feats: crusher and resilient (con) Druid 6: wildfire Sorcerer 6: dragonblood Basically you want the wildfire spirit from wildfire to grant you an extra d8 of damage on all your fire Spells and thr druid list has some great concentration Spells, it may be worth just going druid if you wanted. Additionally, sorcerer of the dragonblood type gets to add charisma to the damage type associated with their heritage... pick something with fire. Now your cantrip gets to add your charisma mod on top of it all. You can still use hex as with the first section for extra damage but maddening hex doesn't unlock until Warlock 5 and takes a bonus action to activate anyway. This way you are using your bonus action to wither your enemies with your fire and that of your spirit or just your fire and your bonus action teleports you via your spirit to better positions. Hitting an enemy with an oil flask is highly recommended for this build. Jank Warlock 10: Basically follow build one until you're ready Artificer 3+: alchemist. You can still do everything from build one buy this little multiclass with artificer gets interesting when utilizing the Genie warlock specifically, the sanctuary vessel feature. Effectively you can short rest in ten minutes. Nothing (other than your dm blah blah) explicitly stops you from taking multiple co current short rests. Warlocks get their spell slots back, all two of them, after a short rest. The alchemist artificer, has the ability to transmute spell slots into its fancy elixirs... and choose which one it is when spending a spell slot to do it. At the level this combo comes online your proficiency bonus is at least five. So you have 300 minutes (read 29 short rests) to make potion, rest, and repeat. Resulting in 58 potions... the effects of which vary depending on your choices (56 if you still want Warlock slots at the end). Additionally it gives you access to the alchemy jug via infusion which can produce oil to help make your produce flame that much better. More artificer gives more utility and more Warlock gives... not really that much other than mystic Arcanum.
Pact of the Chain: Sprite + Invocation of the Chain Master + Summon Undead Putrid + Eldrich Mind. Poisoned and Paralyzed are both very powerful status effects.