Divorce after Twenty years together Community Group
I want to start something for those of us that were married for a long long time. I think that we face a little different issues than those who were dating for a few years or even married for shorter period of time. Being married for so long we have older children some have grandkids dealing with teenagers and their reaction to the divorice empty nesters dating after 40...

That is pretty much standard language in a separation or interim (pre-divorce) agreement. Don't overthink it. All you are doing is saying the marriage is over and both of you are free to do as you wish. No worries about accusations of immoral behavior and no fear of being accused of adultery (because technically, until you are final divorced, you are still married). xoxo
You absolutely BETCHA you want that non-modifiable clause in the agreement. The appropriate language may vary from state to state, but if I get a minute, I will send you the language from MINE via Private Message. I remember it says something about "cannot be modified or rescinded by the court."
Sounds like you're on the right track. But I can almost hear your stbx screaming all the way down here. THEY ALL SCREAM when they realize that being an Assclown is going to cost them dearly.
AT this juncture, I think I would finalize the Agreement with YOUR attorney and then let it be sent to your stbx's attorney. I would not discuss it with him. Period. Let the attorneys hammer out the details.
STOP thinking penny wise and pound foolish, my dear!