DS1 has ASD and dyspraxia. He generally functions at quite a high level... until he doesn't and even though the impact of ASD is lighter on us than many families, just having the ASD diagnosis is recognition that at any level the difference in behaviour has a significant impact on life. And it's wearing. Behaviours that most children grow out of persist. DS2 is quite ditzy too and I suspect there may be something more mildly neuro diverse there. It's draining having to think in triplicate over trivial stuff all the time, and when DS1 is in one of those moods, he doesn't snap out of it, it's like treading on eggshells. DS2 is so much easier to defuse.
So you're ground down and this year has deprived you of the usual respite that probably keeps you ticking over (school/ grandparents), and it takes a good while to get over burn out anyway.
As PPs have said, there is probably depression in there, and that is the easiest sticking plaster to address and stands a good chance of helping you deal with the deeper issues.
The shit dad/ husband needs dealing with. He needs to do his fair share, and his responsibilities putting back on him.
Tell him you are going away for a night or two and do it. You don't need permission, and what else is he going to be doing at present. Hotels are avaliable. You don't have to go far, just a quiet room for sleep and peace with no obligations.
If you do not have fair access to money, then financial abuse may be an issue. (Appologies if it's not financially viable for either of you).
You need some SEN support. Some of the crappy answers by the happily child-free or parents of NT children show how many people clearly don't get it. Even if it's just venting on the SEN board for some relief on here. FB groups can be good too. Face to face even better, but may be logistically tough at present.
These are tough times and you have multuple factors that make it unsuprising that it's a struggle right now 
Parenting isn't easy and no one knows that they've got a SN child on order, and it can take years of additional strain before even getting a diagnosis!