my opinion...not legal, not religious....but to my understanding marriage is an arrangement between TWO parties - often vows are made, verbal statements made to each other and witnesses of how each of them will uphold that arrangement.
it only works if BOTH parties remain invested and true to those vows. if one has checked out - be it drugs, booze, hookers, financial destruction - there is no longer a mutual arrangement.
you can stay if you wish but this is what you get. he's not even remotely interested in getting better. he is verbally abusive. has ditched hygiene. no longer works. has a long term history of drug abuse and addiction.
you also have a commitment/obligation to your child. only it's not an arrangement....the child has NO choice in the matter and is completely dependent upon the adult to provide for them. 3 year olds aren't "best friends" they are children, little babies. and they are at the mercy of their guardians decisions.
your husband did not PUSH you to seek out other male companionship. that was a choice YOU made, a way you chose to deal with your situation. yes he is not giving you what YOU need or want in a marriage...but what to DO about this is on you.
you can take back your power, and the direction you want your life and your child's life to go. or sit around another 10+ years hoping maybe "he" will.....we are the masters of our own lives and can live them as happily or miserably as we choose. make this about YOU dear....God gave you one special life to live as well!