Get EVERYTHING in writing! If he is offering to pay the car lease and buy you a new one when it runs out, have him sign a paper and get it noterized. Anything he says he is willing to give up, give to you, or pay you, get it writen down!
Get your name off any joint credit cards, and make sure he can't open up new ones in your name! Call the credit brueaus and have them block your SS# so no new accounts can be opened. Trust me on this, and here's why:
My best friend's parents divorsed when she and her sister were in high school (he was having an affair with her mom's best friend, prince of a fellow!). And this right after the mom used part of her inheritance from her own father to pay back his company money he had been stealing for years so he wouldn't get fired or go to jail!
He was so desperate to get out of the marriage ASAP that he signed over EVERYTHING in the house, except his own personal clothing. The only stipulation was that when/if she sold the house, he got have the profits from the sale. He walked away with the clothes on his back, and nothing else. He had agreed to pay child support until the kids graduated high school, and he agreed to pay 2/3 of all college costs (mom to pay the other 1/3).
But, on the "way out of town" he emptied his own daughters savings accounts, ran up the mom's credit cards to the max, then tried to sue in court for half of the remaining inheritance she got from her father (it was in a trust, so he couldn't touch though). Eventually he did have to pay back his daughters the money he stole from them, but mom was stuck paying of the credit cards he ran up.
Then, when my friend was in college, he refused to pay her college costs as agreed because she went to an expensive ($20,000 a year) private school rather than an $8,000 state school. The judge not only made him pay, but told him if he tried to fight it again, he'd make him pay it all! (and all this happened while buying his new step-son a brand new Jeep).
In short, because my friend's mom had it in writing, he wasn't able to pull nearly as much cr@p as he would have without the documentation.