That’s really tough and I admire you for what you’ve done. I really don’t have any bettwr advice than what’s been offered already but wish you and your family the best in dealing with your nephew.
Sorry to hear about what you are going through. Never fully write them off, but it seems like you are making the right call.
As long as he's not at risk of getting traumatized in jail, not bailing him out isn't the same as cutting him off. If he's visibly angry at you or family and weaponizes it as guilt, then yall will have to learn the art of laying down boundaries. You've probably shared among family about the nephew's gaslighting and tailored sweet tongued lies. Tough love is usually better than enabling the person in the long run, but with emotions involved, it usually goes t*** up. So yeah, talk to other families going through the same thing through support groups. Patterns show up, and you might see a plan that works for your family. Better than running off the hip while getting pulled by guilt or rage.
It's sucks being tortured mentally, spiritually, physically, emotionally and financially. Man if you have genuinely tried everything and your drowning in a toxic pool of sh*t and your health is suffering, turn the f*ck around and walk away. I speak from experience, good luck.