Hey Amber,
I'm so sorry to hear about what you're going through. You've got an awful lot on your plate and your in-laws aren't doing anything to alleviate the burden on you.
Whilst I don't have any strategies or words of wisdom for you, from my experience in dealing with my A's parents, I've learnt this:
1. Parents can be the best enablers - paying rent, bills, etc. I've found that my A's parents knew that by cointinuing to support my A (doing washing, letting him sober up when he needed a place to sleep it off, financial support, etc.) everything could 'continue as normal', meaning that th A never hit rock bottom.
2. There's a level of shame associated with admitting there's a problem. For example, my A was never an 'alcoholic' he just 'drank heavily and sometimes got into trouble'. When you're missing two weeks of work and don't call in sick during that period, there's more than just 'trouble'. His life had spun out of control.
3. Blood is thicker than water. Sad but true. It didn't matter how supportive I'd been, how patient, how caring, when the rubber hit the road, and they needed someone to blame, it was me.
I really feel your pain and frustration. Sending you lots of love and strength.
Xxx