bless your heart, it sounds like you are in SUCH a tight spot! but you have been strong, and i bet part of the reason you are so bummed out and depressed right now is that you are actually facing up to facts. yay for you; but i know it really sucks to look at how things really are/have been.
i also have been in an abusive situation for four years, and i'm pregnant with my third. i don't think my situation was nearly as intense as yours---mainly verbal and emotional abuse-----but the very BEST thing i ever did was leave a few months ago. i don't know why i didn't before, and getting to that place is something only you can do, but i highly recommend getting away if only just to get a break and clear your head! it helped me so much!
oddly, my husband complied with all my requests---- try to check yourself in, get into counseling, go on medication, go to marriage counseling and really work on it, NO selling drugs(!), no sleeping until 2 p.m., stop blaming me for your problems, etc. i was very clear, and he has done them all. we got back together after a month, and he is working hard at changing, and i have stayed. our relationship is starting to blossom again, but he knows that if certain behaviour surfaces again, the kids and i will be gone the next day, because something changed in me. i don't know what it was, but i am not the same woman that stayed for four years because it theoretically was "getting better".
i pray you will find strength and wisdom to keep on, for your children's sake, and because YOU deserve to be in a healthy relationship. i hope my story is at least sort of helpful. and i agree with PP, if you were out of the situation, your children would be in a FAR worse situation......
hugs