OP just so you are aware too, you mention the baby's father and say that he has a number of issues that you feel would make him unsuitable for parenting a child
You need to understand that in care proceedings, parents with a whole plethora of issues, drugs, MH, DV are supported to evidence that a) they can make and sustain changes b) they can meet baby's needs
The father (if he wished to present to care for the baby) would therefore be assessed and supported with a number of interventions (if he chose to take them up) to determine whether he could provide permanence for the child. The same would count for any family member who presented to care for the child.
We do complete viability assessments for family members who present, if they are negative (which means we wouldnt normally propose further assessment) we are increasingly being ordered by courts to continue with further assessment despite the SWs recommendation. Obviously that doesnt mean the final assessment outcome is positive but it means that proceedings are lengthy and protracted with contact taking place with the family members being assessed to determine their suitability etc etc.
In addition, children return to the care of their parents on regular basis where things arent perfect, we accept that some parents live with substance use, alcohol use, some poor functioning. If the assessment is that this doesnt affect the child to the degree that significant harm is caused, then the child will remain with their parent (or be placed with the alternative parent if thats the circumstances).