If it will help you more to write the letter than not to write the letter, I would do it.
My first thought was it will just add fuel to the fire of his selfish "Let's make Pippi suffer"
doing it wouldn't be helping you since from what you've reported, he seems to thrive on
making you, in particular, angry and upset.
But if you feel there may be a documentation payoff when it finally gets to court, that's something else.
If by pointing up the date he listed the property for rent, enumerating the many luxury things he's able to afford, and calling him out on his lies
will actually be useful getting you and the kids a better settlement someday, I
certainly would do it.
Then there is the PO factor ("pizzed off" for you neophytes to legal jargon
)
You sound like you need to vent this and let him know where you are.
Like you said in your other post, you've become the hero and not the victim in your story now,
and it sounds like you want to warn the bad guy he better shape up or else.
I get that too. Just be strategic when you release information, because you
know his legal team will parse it out to use in their own interests.
So be the smartest angry hero you can possibly be.
I wish I could help you out from my end by carefully keying
each panel of one or more of his expensive cars.
(OK SR police, just joking)
I don't like this guy either and I've never met him.