YANBU. You can't go uprooting the kids for a 'backwards step' job for DH, especially one you know he will be unhappy in & on top of that doesn't pay enough. Yes you can get a job, but then who will do all the ferrying around of the kids, school holiday care, wrap around care etc?
Just a few of my thoughts, you don't have to answer them if you don't want to 😊
It costs a lot of money to move a family back, in both actual costs & setting up costs etc. If you are just scraping by, can you afford to do it?
However, I do think you need to make some plans. You are rapidly approaching the point at which you moving will affect the exam years schooling of the children and shockingly quickly they'll then be of an age where they could choose to remain in Europe if they don't want to go to Aus.
Where do each of you want to live?
You have 3 children rapidly approaching exam years - IMO you need to decide is that's where you are, back in Aus or elsewhere.
This is a BIGGIE - Your DD has got a place at a Gymnasium school - there's not be in Australia. Are you sure? Can you justify denying her this place?
You can't work where you are. Will you work if you go back to Australia? Doing something in your career or just so,etching that earns some money?
You can't study what you want to where you are - but do you still want to? Do you think you could - time wise, financially?
Can your DH not get a better paid job where you are?