OP, you have a huge H problem. He will not set appropriate boundaries with his Ex or younger DD, and he expects you to suck it up. He gains validation in ways that are highly disrespectful to you.
H is pushing you to develop a friendship with this horrible woman who:
*Spikes your drink with alcohol which could harm your baby
*Intrudes in your personal business re contraception
*Goads you with a description of H’s proposal to her
*Negs your wedding dress and baby’s clothing
*Is needy and demanding, always pursuing both H’s attention and more money (per previous thread)
*Won’t stick to the contact schedule and expects accommodation, but wouldn’t dream of ever reciprocating
You’ve said that after years of frustration, you trained yourself to think of Ex as an insignificant background noise, but compartmentalizing her toxic behavior can take a serious emotional toll on you.
And that’s not your only H problem.
He allows his 12 year old DD to be an imperious diva in your home and in public, and expects you to shut up and take it. You understandably dread her coming. She is consistently rude and demanding, and you resent H’s refusal to acknowledge and address her behavior. She won’t say please or thank you, criticizes everything, and demands/gets whatever she wants. Whatever time and expense are spent on activities for her each Disney weekend, she is contemptuous. When money went missing and was found in her bag, H wouldn’t hear that she took it. When she didn’t want to return to her mum’s and the £300 car key went missing, he wouldn’t even consider that she hid it. You go out of your way for her (even letting her pick the baby’s middle name), yet are not allowed to set boundaries or even call her out her rudeness, and she knows that. When you attempt to address her behavior with H, he shuts you down. Thankfully, his older DD is a kind, lovely girl with whom you get on well.
You have the right to be treated with respect. I wouldn’t subject myself to this maladaptive enmeshment that tramples on your boundaries, nor would I raise my child in this environment. Think carefully about the relationship blueprint that is being modeled for your son, and about your and H’s differ parenting styles.
As for H’s agenda for you to befriend his Ex, she is a nasty piece of work who tried to hurt your baby, and she gets a buzz from putting you down and trying to throw you off-balance. It is troubling that H is seeking gratification by your weakening your boundaries to bond with this viper. If this new thing is being driven by her, you can bet she has intentions to diminish you and escalate their codependency.
You recently wrote that you always felt you were behind your peers, and were glad to settle down at 30. Lately, though, you’ve been feeling trapped, lonely and unhappy (though you adore your baby). You are now in a different life in a small town after living in a city. You were recently upset and envious when your younger, single, free brother left after a visit. Perhaps this restricted feeling is due in part to your feeling powerless, disrespected and unheard in your current life.
You need to make some major changes.