First of all ... know that I am sending out good thoughts to you and your children and trying to send 'em to JBT too

.
I totally understand about sending letters. I'm 100% behind that although I wish that it would only be your lawyer and not you. You can show that you are still trying to keep the communication lines open through your lawyer without setting yourself up for DAMM lying about what you have said to him and what you have not said to him. But if your lawyer, who knows JBT the best, says that letters from you personally will make you look better in his eyes, then by all means do it!
I know that I might be beating a dead horse over this but I still don't "get it" about skipping the next scheduled visitation. I think that you are letting your short term goals of keeping your kids with you over the summer override what should be your long term goals.
I think those long term goals are threefold: (1) Proving that you are a mature, caring and cooperative parent whose primary interest is her children, (2) Proving DAMM to be the liar, manipulator and abuser he really is and (3) If that can't be done setting up a drama and stress free visitation schedule set in stone. I don't see how keeping the kids on that weekend furthers any of those long term goals. In fact, it will set those goals back! You will look like someone set on revenge and DAMM will play the victim again. You KNOW how much JBT loves the father-victim figure.
OTOH, if you send the kids you will look to be acting in the best interest of your kids. If DAMM keeps them after your letter spelling out visitation then he looks like a manipulator. He is the one who looks uncooperative. He is the one who is increasing the stress on the kids and putting
his need to hurt you
before the
needs of his children.
Mulan, give DAMM the rope to hang himself.
You were ready to allow your kids to go with him for 5 weeks straight (as per the agreement). Allow them to go with him for the July 4th weekend and if DAMM keeps the kids until 7/14 all the better for you! As for being thrown in jail, I think that's a red herring. I don't see how you would be thrown in jail unless you thumb your nose at DAMM and JTB by denying DAMM visitation on the 4/4 weekend.
After saying "Listen to your lawyer!" again and again I feel bad second guessing her. She may say that it was her advise to keep the kids that weekend, but in the end you are responsible for your own actions. Please think about what you really want out of the next hearing long-term and communicate that to your lawyer and then ask her if keeping the kids will really help those goals. If she says "yes" then I will bite my tongue for the next 2 1/2 weeks.
One more thing ... don't count on DAMM to not to re-hire his attorney for this hearing. He's not stupid.