The realme, all these things you are feeling and fretting about are quite normal. It is a very good sign that your little boy is able to openly talk to you about his feelings.
He has possibly herd his stupid father talk about 'killing himself' and has just picked up on the idea - he will have no real understanding about what it means. He is unburdening himself to you and all you can do is hold him close, listen, reassure him and tell him that his life is going to be fine. Can you let his school know what he has been saying so that they can show him a lot of support and encouragement?
You have been holding things together. Remarkably well. Yes the future seems scary and the responsibility seems enormous. This is because you have a genuine sense of responsibility - not a fake outward show of it like your NH.
Calm down. Your bitter feelings about your ex will fade with time.
But remember - he is not living a jolly life. He is living a half life or no life at all really. They are automatons seeing life and events through a prism of their own selves as in: 'What is in this for me? What role can I play-act now to garner sympathy or admiration or respect blah blah?.'
They don't have the pleasure of having deep human emotions (be they good or bad, feeling - really feeling - is what it means to be human after all)
Let him say whatever the hell he wants to his therapist. He will think the therapist is bloody useless anyway and will stop going very quickly. It is just for show again. 'Poor me, my bitch of an ex has driven me to therapy.' He will try to manipulate the therapist.
None of it matters to you right now (or ever) because as you say, you have your own life to re-arrange and get some laughter and focus back into. It has only been 10 weeks my love. This is bugger all. It is a nano second. The fact is yu are still standing, your dcs are secure with you (ie your lo opening up to you and crying.)
Tee is fall-out from this shit - bt there wold be fall-out even if there weren't the added complications of a lying, twisting N in the picture. Just keep going.
Perhaps you can join an art class of some sort? I did art and pottery classes when I first hit depression and stopped working (which is when my exnh started the devaluation phase - I was no longer a 'prize' in his eyes, just a flawed ill person who he was totally unable to help or support. Twat)
By the way, I spent a couple of nights on the nut ward while I was with him too. He drove me to attempt an overdose but when he turned up to 'visit' me he looked like a ghost in shock. And guess what? When I had to go back and see the psych team after he finally ran away, they mentioned how oddly he had behaved back then...how he didn't seem to understand or care what about what I was going through.
So they saw right through him. This gave me enormous comfort.
You are not mad my love. You have been made to 'think' you are mad and crap. Gaslighting. Manipulation. All the other key words...he has done a really good number on you! But you will get over this. It is going to take time and a lot of healing.
But you are a bright, caring and loving woman. You have been abused.
Have you read the Lundy Bancroft book 'Why does he do that'? I m reading it right now and it is really brilliant.
try to lighten the mood with your dcs...take them to a castle or for a trot on a horse. Buy a puppy.
You will get there. You are doing just fine.