Hi OP. What I'm taking from your post is (correct me if I'm wrong) -
You both work 4 days a week (the same days? Mon-Thu?)
Your lifestyle is built primarily on your salary, as it is hard for DH to hold down a job due to MH - so this causes you to feel trapped shouldering all responsibility for the mortgage and bills in a job you really don't enjoy.
You feel like your life is one long groundhog day of the same things day in, day out, chores, laundry, cleaning, cooking, shopping, etc. And your weekends get sucked up with a lot of this.
Then when you take any kind of annual leave, it's primarily used to visit family to please them.
Firstly, I think it's actually sensible to base your lifestyle on your salary given the situation. I have ADHD and have had mental health struggles also (kind of goes hand in hand), and I find it extremely difficult to hold down a job for more than a few years. So in our household, we base our lifestyle on DP's salary BUT I pick up the slack in other areas. I work fewer hours, and I work for myself - and we just treat my income as a bonus. Could this be a possibility in your house? Could DH reduce his hours, do something he can manage, and be the primary shopping / cooking / cleaning / whatever person? Is there any way you can change anything about your lifestyle to release the financial burden on yourself?
If that's not realistic or desirable, then are there any other solutions? Can you outsource and automate things? Hire a cleaner, order groceries online, have meal boxes like Hello Fresh / Gousto (if they have them in Aus) 3-4 days a week?
Can whatever chores need to be done get sorted during the week, or on one of your three days off, leaving the weekend free for pure fun stuff? This is what we do now. All chores get done during the week, shopping is done on Friday, Saturdays are for fun days out, Sundays are 100% for chill time, self-care, etc.
I feel like what's happening is that your life ticks all the material/surface boxes but none of the meaningful, joyful ones. The world is a playground! So much to see, explore, have fun with. And you're locked in a cycle of laundry and drudgery.
I think you really need to sit down with your DH and communicate the depth of what you feel. No accusations or blame, but tell him how sad you feel about life. Come up with a plan together. The situation has to change. Go through every aspect of life you are unhappy with and work on a solution to each. And start taking space to explore life and find what you enjoy - then take space to enjoy that daily, weekly, ongoing.