Drug abuse, my sister and my suicidal father

So I now have two jobs and I love one of them... but that is a lot of stress. meanwhile every time I visit my parents I am bombarded with my dad saying things like " when I die make sure you look in on your mom ok? I dont want her to be alone." "I hate my life" " everyone would be happier and better off without me" " I am a worthless piece of shit" all because he hurt his back and cant work because of it, and needs disability... and he is very dependent of pain killers and taking them by the handful... And my mother crying to me about being sick and not being sure she can handle my dads shit, that she cant get sad at him talking about dieing or she is being a bitch and doesnt love him and all kinds of crap.

And my sister... ( mother of two of my wonderful nephews and my amazing niece, step mother of my other niece and nephew) got one of the best jobs offered in my town and quit after a week, she is living in my parents garage and leaves her children all the time to go get high and is selling her foodstamps for pot money. I try to tell her to be a responsible mother and she just gets pissed at me and wont talk to me. Meanwhile my ten year old nephew ( after seeing my sister smoke pot almost daily since his birth) decided that it was ok for him to smoke pot. My sister being the ultimate hypocrite told him that it was wrong and made him research all the bad shit it will do to him and to a young mind. I cant stand how she will talk to him like that and still go out and buy the shit and smoke it at my parents house!!!! meanwhile her kids are growing up thinking that violence and drugs are a normal part of life and that are being neglected by her and my parents ( both college students, and my father trying to work part time despite his injuries) are supporting her, her jobless fiancee, her three kids and her two step kids in a three bedroom house while she sells off her kids food money...

I want to help my family but my husband is not comfortable helping my drugged out sister and all her kids when she should be being an adult and taking care of them herself and my dad just gets more depressed and feels more depressed when he has to barrow money... I am so stressed and so worried about my family and I just feel lost and angry all the time... and helpless on top of that... I just want to get lost in my mind but with two, jobs, of husband, and a failing family I cant even manage to pull my head away long enough to lose it for a few minutes.