First - What you really should tell her I think, is that if she doesn't put forth the effort to try to succeed in life she's going to fail.
Tell her that if she comes to you for help, and takes none of your advice and continues to whine and complain, tell her that until she gets her act together and starts acting like an adult, that she's wasting your time by asking for an easy way out.

I personally have no job, no money, and I'm terribly underweight... but at least if someone offered to help I actually try... though just trying to stay sane atm >.<
She needs to take responsibility for her actions. By declining those phone calls, she's basically saying she wants to leech off you... =.=

Second - Maybe if you made arrangements for a friend to take him in until you move out? Or maybe if you have any source of income bribing her might work...

Just throwing a dog away like that is horrible... because it loves you... and when an animal gets attached to someone it causes a lot of pain to just... vanish from their life...
Also, having been through so many families... the dog is going to start developing trauma from this I'm sure, and stop getting attached to people for a really long time...

I think having a friend possibly taking him in is the best bet though. =) best of luck... hope you can keep him ^_^

Third - Hmm... as for biting nail stopping, one thing I've heard work is find something that goes on your nails that tastes REALLY bad... and after getting that nasty taste in your mouth all the time from biting your nails, you'll naturally stop because it wont be worth it.
Also, it's probably being caused by stress... which I'm noticing you've got quite a bit...