Hang in there Lost! Your H is hurting, and he is medicating his pain with alcohol and other things. The more you give him space and leave him alone the better. I know for business matters this is tough, but the more you remind him of bills, etc. you become the nagging wife he hates. The courts will make sure he takes care of loans and all that anyway. Try to separate finances as much as possible, but when you have contact about business stuff, be cool, calm and collected. He will notice the change, and that you're not needy and falling apart, and it will surprise him. Hang in there!
Others can chime in here, but I don't think it's healthy to read his letters to your daughter. They weren't written to you. Personally that would hack me off if I were him. It's probably better for you to be relieved that he's writing her, and leave it at that.
Well, I'll chime in. He's writing emotionally abusive letters to his children and you're all they have left to alleviate that. I think you need to know what kind of psycho bullsh!t he's pulling on the children. And I think you should keep them for the courts. If and when you come to custody issues these letters are IMPORTANT.