Advice from CF stepparents on how to remain in alignment

I'm CF and my SO has two kids who are here EOW and 50% or more of school holidays.

I don't want my own children and I'm naturally independent.... even more so in this relationship. Due to trying to maintain my own life, issues with HCBM, and a variety of other reasons, I NACHO.

Weekends the kids are here I often do my own thing - gym, drinks/dinner with friends, travel etc. I travel a lot on my own, SO is unable to join due to finances.

If I have an event on a kid weekend I usually go alone as the amount of stress trying to organise SO's parents to babysit is not worth it - the family all procrastinate and no one agrees anything till the last minute. Swapping a weekend doesn't work due to HCBM. So, I've stepped way, way back

The question I have is how to CF people maintain alignment in these situations? It's like we're leading separate lives at this point. I assume he won't be attending weddings, long or short haul trips, dinners with friends, etc. I don't attend his family functions anymore due to some very complicated things that came up with his family. We do some things together, occasionally have a date night, and spend some time together with the kids but again, it's complicated. I've had to put a lot of boundaries around me.

I genuinely didn't realise how easy it was to fall in this dynamic given we're not on the same page particularly with me as a CF person. Curious about other people's experiences and how you make it work