My mother is a classic narcissist, my DF was a classic enabler, not scared of her but conditioned to take her side, take the blame and try and smooth things over for an easy life. The thing is the man was a man of his own mind and didn’t take shit from anyone in every other aspect of his life. But the relationship of couples, cohersion, abuse, controlling, manipulation is very very different. It sounds like your FIL has been conditioned to do her bidding and even take the fall for her, just like my DF did. To me a parent should protect their child, my DF either didn’t see, dint think it was that bad or thought he was doing his best to be peace keeper, but none of it protected me. Had I brought it up, I doubt it would have made a difference.
The drinking I don’t think is a big issue. I come from a family of big drinkers, work hard party hard. Drinking all day is common throughout my wider family. Very much functional “alcoholics” if that’s what people want to call them. I doubt that is her issue at all as the drinking culture dosnt impact the general family life of my relatives, any issues are individually related.
The young grandmother thing could be a thing, especially if she had children young herself and wasn’t the best mother. My DB & SIL were disappointed in their DD having a child in her early 20s, as were her BFs parents as both set of parents had children in late teens early 20s and wanted more life experience for their DCs. Everyone came round fairly quickly though. But it got me thinking about someone I know who refused to accept her first grandchild. Her son got a girl pregnant at school, she refused to acknowledge the child’s existence, even to this day, he will be in his 30s now. It was because she thought she was too young to be a grandmother, like your MIL she went to work and partied with her friends, was never the best mother. The next grandchild was not allowed to call her Nan, gran or anything else other than her name. Now she is all gushy over her younger grandchildren by the same son who had the first grand child. To this day he has never told his mum he started paying maintenance (willingly not forced) to his child and she has no idea that him and his sibling had a relationship with his child when the child was young.
Personally I’d stop letting her fill my head as she’s winning. Let your DP take a step back, get on with things. If FIL wants to see you say fine. If he says don’t tell MIL pretend you haven’t heard him, don’t mention her, if he tries to make plans for another bbq say whatever, if he mentions mother son time say great she knows where we are and most importantly tell DP to STOP trying to contact her. As he said it’s like he’s chasing her and he should not have to do that.
I don’t think you or your child are the issue from what I’ve read. The woman clearly has issues, if it’s with you she needs to grow a pair and tell you to your face, if she can’t she’s not worth bothering about.
Im NC with my own mother, it’s absolutely the best thing for my children, so don’t think your DS is missing out on something as some people don’t deserve to have children or grandchildren. You just do your best by him and don’t worry about anyone else.
In your circumstances though I think I would say to FIL, your priority is your child, your happy for him to be around but if he starts stopping coming then wanting to come back he can’t, he’s either in or out of your child’s life. Don’t make it about mil, purely him and his decision to be a grandfather or not.