Marijuana vaping is legal sa ibang parts ng US for recreational use. For medication usage, halos legal na yun sa buong US. You mentioned suicidal siya (dahil sabi mo pag iniwan mo siya magtatangka siya), is that part of his medication?
As for the money, if you are getting $300 every 2 weeks, that's 30,000/month. Hindi pa ba sapat yun para sa 6-month old na baby?
I think ang pinaka magandang gawin mo diyan is mag usap kayo ng masinsinan. If hindi ka nag aagree sa ginagawa niya at ayaw niya naman tigilan, you always have the option to leave him. Kahit US resident siya, he is still the father of your child kaya required pa din siya magbigay ng sustento. Whatever he is giving you right now sounds fine to me para sa 6-month old na bata.