Sadly, @Sadgie MN posters will mainly defend the female, run down the male and god help you as the paternal grandparent.
I wouldn’t even try to justify yourself or your son’s actions and choices on here. As a prospective young father, your son has already been written off here and can’t win, whatever you suggest, whatever actions he takes. Plan to support his child and he is controlling, plan to walk away and he is a despicable human who does not care.
I am still scarred from posting about my DS, a young primary teacher, whose ex wife prevented him seeing their child. Courts involved, contact repeatedly frustrated. He did everything to see his child, agreed to any contact plans suggested, short visits, slow transitions, frequent contact, contact centre, absolutely anything to continue a relationship. Courts were looking at parental alienation and considering the child being made resident with my DS.
Posters on MN, suggested a huge range of untruths about my DS, defended DiL, blamed DS, couldn’t accept that this was a female unwilling to share their child with his DF. I was questioned and interrogated, made out to be covering. I was vilified for sharing their story, for wanting to offload. I wasn’t involved at all, a choice taken to maintain an objective distance.
My advice would be to walk away from the thread OP.