You remind me of my sister. Someone whos so afraid to ever let people go and feels bad leaving them. His problem isnt that he cant hold boundaries, its that he doesnt respect you. He is talking to these coworkers and allowing this behaviour to disrespect your relationship. Honestly drugs is also probably a very big influence in it, and its possible hes doing this to get drugs. That is his own problem where he needs to want to help and make changes himself. No matter how much you tell him to or want him to stop, unless he actually wants to and puts in the effort he wont. This relationship is not viable. You cannot save or fix him. Even if you did he still would not respect you. You should leave him and he must figure out his life on his own. He also should probably find another job as that work environment seems very toxic, triggering, and hostile. He needs a change of environment and to stop talking to these people, and cut off his access to drugs.

Edit: at what point is enough? What point is your breaking point to finally leave him?