How "open" should our adoption be?

Hi all, I posted something similar in a different forum thread... curious to see if anyone has anything else to add :) Husband and I have been fostering my nephew for over a year now. The parental rights have just been severed and we’re about to go to trial in December. We were told to start thinking about what involvement the bios would have in FS life (if any) and to need to be ready to discuss it at a facilitated settlement mediation. I’d love some input as to what you guys would do (and have done) in situations similar to ours. Let me give you a bit of the background of the bios. birthmom was 16 when she had child, BF was 18. FS was majorly in the care of the father and paternal grandparents before CPS removal (mother only wanted involvement when she was upset at father). FS was removed from BF because of abuse of drugs and neglect and was not allowed to be with the birthmom because she failed to protect. FS went to maternal grandparents, where there was suspicions of abuse. That’s when he came to our home. Both parents were given a case plan. birthmom has not complied to any of it, BF was in compliance except for finding a job. The mother has not seen her son much, an hour or two a month for the first few months. The last visit was in March for an hour. She has abandoned her son but still wishes to be his mother and feels she has done nothing wrong. When asked where she’s been the past few months, she simply said “around”. She is pregnant with her second child. Biological dad seemed to be doing okay until we suspected several drug relapses. Being my brother, I knew when he was using. Our relationship became really bad… he made threats, slashed my tire in attempt for me not to be able to go to court, etc. We ended up getting a restraining order against him. About two months ago, he overdosed (and possibly tried to kill himself) and landed in ICU for a week. He admitted to the overdose in court but is insisting if he had more time, he’d be fine enough to raise his son. Obviously, our situation is complicated because BF is my brother. For the sake of keeping our family intact, we will have to see each other at family functions. We feel BF should be involved in his life but don’t feel we should agree to anything in writing at this point (it’s waaaaay too early in his recovery). Not sure how to handle birthmom though. She hasn’t had much involvement in his life so far and we feel the only reason she’s fighting now is because it’s a battle between her and BF. Any advice you can give? I’m curious to know how the “pros” would handle it ;). Thanks in advance and God bless!