Birthday legalities

Awhile back I sent the STBEX an email with proposed "policy" about the boys' birthdays.  This was in response to the experience we had with the middle's birthday, in which he played the victim card again and didn't come despite that I held it at a neutral location, invited folks using the joint email account we set up for the boys, and made sure to keep him in the loop about everything.  I wanted to avoid the miscommunication that leads to passive aggressive behavior on his part.  So here's what I said:

Regarding #3's birthday.  I think perhaps part of our communication difficulty about #2's party may have come from using language like "I'd be happy to."    Also given our current relationship, it isn't necessarily easy to work together in the old format of just talking about things casually and figuring things out in the office at night.  So, I don't know if we need to write it into the parenting plan or what, but here are some guidelines around birthday parties that could help avoid future conflict:

• Baring other significant conflicts, the child's party will be on the weekend closest to his birthday, with Wednesday being a toss-up. 
• Baring future unforeseeable negative developments, both parents are always welcome at any child's birthday party, and an effort should be made to make that possible.
• Let the parent who "has" that weekend with the boys, have first opportunity to take the lead in planning the party.  (Here after identified as the "lead" vs. the "co-parent."
• The lead may pass on that role and ask the co-parent if s/he wants to either take the lead on the same weekend or on his/her weekend.
• The lead may plan the party single-handedly or may specifically ask the co-parent to do things.  The co-parent can say yes or no to those requests.
• The co-parent (who isn't the lead) may ask (not just offer) to help with specific tasks, the lead can say yes or no to those requests.

I realize it's pretty legalistic, but it seems necessary in this situation.  How exactly did we get here?  

So then he agrees that he wants the lead role for #3's party, and so I don't mention the fact that I've heard no plans yet a week before his birthday.  The weekend before he emails me a sample of the invitation, but when I responded that I was surprised he used his personal email as the RSVP email, he didn't change it.  It was pretty ridiculous, RSVP John Doe, johndoe@gmail.com.  But whatever.  And then it was forecast to pour down rain, and so I, being me, and perhaps not listening very well to my therapist's previous advice brought it up to him on Thursday before the Saturday party.  "Do you have a plan if it rains..." And I gave my (unasked for) blessing for him to move the party location to his house near the park in case of rain.  Why did I do that?  I was trying to be nice.  Trying to be helpful.  Trying to make peace, throw him a bone so to speak.  But why?  That's a good thing, right?  So why is it wrong?  Hmm.  I'm trying to remember why my therapist would say that was wrong other than just that it was unsolicited.  He didn't ask for my help.  He didn't ask to be rescued.  So I should have waited to see if he asked for help.  But again, why?  Is it just because we need to shift our relationship to one with markedly different patterns, or is there a reason that goes beyond our relationship, that's affects my relationship with others in general?