Your topic could have been mine. Even worse, I had told my husband very early on in our marriage "Don't worry, I'm strong. I can cope with anything." I was very wrong. FYI, he has chronic knee, lower back and now groin pain, in addition to having had anxiety, depression and ADHD. And he hasn't worked full-time since a few months after our eldest child (who is now in uni) was born.
Finances dictate that you need to go back to work, although I would apply for NDIS and the Carer's Pension (as someone else has suggested) with a support worker or social worker's help. In the meantime, you need a plan as it can take weeks or months for Centrelink to process your application. And you still might not get it.
You and hubby have a role reversal. You are feeling bad as you are trying to fulfill almost all roles, and that is just near impossible.
Your husband is now a Stay At Home Dad, for health reasons, and he needs to embrace that role. It's good he's doing the pickups and drop offs. He could take over school lunches too, this is not a lot of work.
You are now the Breadwinner! It's not something women are well prepared for in Australia. But, if you stop thinking about trying to do all the other stuff you used to, it's not so bad.
You will need help with cleaning, etc. that you don't have time to do and hubby can't physically do. I can only afford it once a month, but I do have cleaners come and thoroughly clean the bathrooms, floors, etc. Because I just can't bring myself to do it after working 40h a week and commuting an hour each way!
Best of luck and keep chatting - it helps.