What would you do. co parent with narcissist?

So I have a parenting plan with a narcissist yes he’s been diagnosed with narcissism. we both live in different states and I have to pay half his plane ticket and he pays less child support than what he’s supposed to due to helping with travel costs. I’ve asked my lawyer plenty of times and he’s confirmed it’s it’s just half the plane ticket and it says why he pays less in child support in the paperwork.. however my ex does not think this. We have to use a special parenting app to communicate only. Due to past abuse that way it can be documented if the courts need it. Well a day or 2 after the visit I get a message that looks like this

* this is just an example not actual message

Travel Expenses

Gas: to/ from airport exit 250 (names) car
$34.50 (35 miles)

Air port parking:
Line 78 parking spot 2

Air ticket to/from location (names ticket)

Rental car: Jeep Wrangler hybrid

Gas for rental car: Jeep Wrangler Hybrid
($101.00) full tank pick up/ drop off (535 miles driven)

There is more but you get the picture..

So at the very end of the messages I always get “total balance $1500”

I’ll pay my portion like it says in our parenting plan. And the next messages come.. “$260 payed via venmo out of outstanding balance when will you be making your payment”
I ignore it I only communicate if it’s about our child, then it’s always a week later, the abusive messages comes. “This is my fault” “you ruined my life” “do I need to take your child support away” “you can’t read a document right” “I’m gonna watch you like a hawk for 18 years” it goes on and on and on and on or he tries and changes the parenting plan. I just ignore him but this have been going on for 2 years and it’s getting worse. I’m tired of the abuse messages and him acting like a bank collector. What would some of y’all do? Please no rude comments just want some advice.
What would you do. co parent with narcissist?
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