And I thought the relationships with my sisters were bad!
Good Golly Miss Molly!!!!!!!!!
You need a break for sure...BUT you need to try to get her some help, some way! Go online, find a way to hook her up with a Doc/counselor who is willing to go to her (?) I don't know your or her finances or insurance but she definately needs help & you can't keep putting your dayz & nightz on hold to listen to her everytime she calls.
She is the WRONG person to be caring for this child, sounds like he is already headed in the wrong direction spending time with her certainly isn't going to help him!
Get some rest, try to 'regroup', then get serious about getting her help, if that's not possible then...love her...BUT don't forget you have a life, we all choose our paths, sometimes we have to put ourselves first & our own kidz...