JMF, I don't believe I have ever met anyone quite as stubborn as you are being. You know the checks will bounce BUT you take them anyway? Now I am letting my AD use my car because we cut off the insurance on hers tii there is money to reinstate it. But as I recall he didn't want to fix your car he just wanted the money?
I couldn't afford to keep cashing bad checks, I know one it would hurt me too much emotionally but financially why do you keep doing it to yourself?
Your daughter does sound stronger then you are where her brother is concerned. How about asking her to help you say no to the checks? Not sure how but man you just have to get a grip here and stop jumping in the quicksand. Prayers are helpful but in this case I will tell you "God helps those that help themselves". (((HUGS))))