I am going to throw out another, perhaps controversial, opinion on the child support. Keep in mind that I am very bitter right now, so maybe this should be taken with a grain of salt.
While I agree that your baby (and all babies) deserve to be financially supported by their fathers, absent or present, I feel like in this situation filing for child support is only creating unnecessary ties to BD. We have established that he is toxic to you and toxic to the baby...I would just distance myself completely. At this point he is not on the birth certificate and has no parental rights, which is a good thing. I would leave well enough alone, especially considering the fact that he has no means to pay the child support so you would probably incur lawyer expenses and time off of work to attend court hearings for naught.
I think you have a chance here to actually be rid of him, and you should take it and run with it. Read the stickies at the top of the page...manipulation is a common theme for addicts. He's not calling you after all this time because he loves you. He's calling because he has run out of others he can manipulate. It is impossible for those in active addiction to love.
Sorry if all of this is coming across as harsh. Like I said, I am a little bitter right now. I don't mean any of it in a negative way toward you. I think you are doing the right thing in a very tough situation, reaching out for advice and information. I am just speaking from my own experiences and lessons learned.