You have my sympathies op 💐
Its a horrible feeling when everything is so stressful and you don't even know where to start fixing it all, so end up never starting.
Break your problems down, some you can't do anything about, but others you definitely have control over.
First thing I would tackle is your dh. He should be dealing with the kids, if your bathroom smells - well he uses it too so why can't he do it? He needs to know how you're feeling and that he needs to step up.
How far are you into getting a diagnosis? Have you tried posting on the SEN board on here, or even in chat for parents with more experience for tips, ways to help with him being overstimulated etc.
The wait for physio is ridiculous, could you maybe Google for some techniques to try at home, they might not work, but its definitely worth trying meantime.
I'm not sure what the problem with your job is and I'm not going to glibly suggest for you to get a new one, it's probably worth hanging in there until you're in a better space with everything else in your life.
With the drinking, you clearly recognise that it's a problem. It will be magnifying the way you're feeling at the moment, so if you can't totally cut it out, then please do cut down.
The gas bill just sounds like the icing in the cake of a particularly shit time. I have no suggestions, but I get it, I understand, and many of us are there too. There are threads on how to try and reduce usage, when you're in the right headspace take a look and see if there's anything you can do.
Its so bloody hard being right in the thick of it with two young, clingy children, especially if you're the only one doing everything, coping with the mental load, and have no respite at all. I, like many others, lost my way, and myself, for a good while while mine were young. It will get easier I promise you op.
Don't think about all your problems as one huge shit pile. Smaller problems, a list of what order things need to be dealt with, and take things a day at a time. You will come through this intense time 💐