WH, Your h is realizing that he is losing or should I say lost control of the situation. The proper place to hold the hearing is in your lawyer's office, since your h doesn't have a lawyer. A for the paralegal present, there is a reason for this because not only is that person there to assist w/copying, etc., but as a witness to all negotiations/talks. This is very normal, nothing shady about the paralegal's presence there at all.
As for popping in unexpectedly, you will need to set some boundaries and have him call before he comes over, kids being there or not. This is now your home and I don't think he'd want you popping over there w/o notice, especially after all the negotiations and divorce takes place.
Yes, your h believes what he's saying. If he didn't, he'd realize just what a fool he is. He's still trying to maintain some control over the situation and yes, manipulate you as well. Soon, all of that will be behind you and your h will no longer be able to call any shots except at the local bar if he should go there.
Go to the hearing, but keep your business hat on and leave your emotions at the door. Yes, your h is desperate and the closer it gets to the time, the more he'll say crazy stuff. Tune him out as much as you can. Your lawyer's got this and he knows exactly who he is dealing w/and what type of man your h is right now. He's seen it many times over.
Breathe, have faith in your lawyer, you and the man upstairs and stay positive.
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.