Reading this, I really feel how worn down you are, especially being forty one and still getting treated like you are fifteen in your own home. I am also studying with disability and money stress, and I know how quickly support from family can turn into feeling watched, policed and like you have no say over your own body or decisions. It makes sense that his constant comments about food and health would start to feel less like concern and more like harassment, especially when you are already doing the hard work with specialists and changing your diet.
Something that has helped me in similar family situations is getting very specific about boundaries, not just saying please stop, but naming the exact behaviours that are not ok, for example commenting on every meal, and what I will do if it keeps happening, like ending the conversation or leaving the room, which is also what a lot of therapists suggest for adult children and parents. When you are financially stuck it can feel like you have no power, but you still get to decide how much access people have to your inner world and how long you stay in a conversation once it turns into nagging. You are not being childish for needing emotional safety in the place you sleep.[1]
It also sounds like you are already clear that this is not sustainable long term and that moving closer to Brisbane once the lump sum comes through might give you both physical space and more of an adult to adult dynamic. Even just having a concrete plan and rough timeline can make the day to day easier to bear because it shifts things from I am trapped with him to I am passing through on my way to the next stage. If you do decide to stay for a while, you might experiment with limiting contact with him inside the house, for example eating some meals in your room or timing shared spaces so you are not around him as much, and saving your energy for study and recovery.
You are absolutely allowed to love your dad and also recognise that living with him twenty four seven is harming your well being right now. Loving someone does not mean accepting behaviour that breaks you down, especially when you are already dealing with injury, health changes and a big career pivot. Whatever you decide, you are not overreacting, you are responding to a pattern that has been going on for years, and you deserve a living situation where you can heal, focus on your trade cert and be treated like the competent adult you are.
