Would it change it for you, if one of the step parents were responsible for the demise of the parents marriage/adultery.
No
The correct time to disinvite him was before you had him write checks.
If someone was to reimburse him for the money he has already spent, that might be OK. I guess mom and bio-dad could split the expenses and still uninvite step-dad (although mom might not go for that.)
I don’t have much experience with divorce etiquette. My parents have been married 59 years. My wife and I are at 32 years. No divorced siblings. Just the in-laws, and that happened when my wife was 2. She joined the military to get away from her mom, and we have seen her dad 3 times since I’ve known her.