Hi there readybrek, I am sorry to read your having a dilemma after only being in the country a short time. Unfortunately I know of a situation (court case) the same as yours and the outcome was not good. I urge you to get legal advice, make an appointment with legal aid preferably in the city where there are more staff, quicker for an appointment and a bigger chance of finding a lawyer who is clued up with the HC and immigration.
The couple split up within a few months of arriving, the family (dad, mum and son) were in AU due to his visa linked to his job. The Dad met someone else within months of arriving and moved out of the rental, the mum got on a plane with her son and brought their son home. HC began and she had to return her son to AU. A two year court case began, she wanted to bring her son back to the UK, but the law stated that she had broken the HC and although she could not legally stay there, the son could still legally stay there with the father, and so she had to apply for an international relocation order. Within the two years of her and her son being there she wasn't allowed to work or claim any benefits, she lived off hand outs and church goodwill. She had to sell the family home in the UK to fund the case.
Now the twist - within the two years of the court case, not only had her son now began school and settled, but she had met someone and changed her mind about wanting to come home to the UK. The courts wouldn't allow it, and after spending over £100,000 on legal fees and then uprooting her son from his father, new life and her from her new partner - she was told she had 28 days to leave the country, with the child. So she came home and is now rebuilding her life again here in the UK.
It is so complicated its unreal, I was also sent back to AU for over 2 years whilst the courts made decisions, I was unable to work or claim any benefits, I suffered terribly and my absolute heart goes to anyone who goes through this.
I hang around on this website to give what little advice I can about this topic, I wish I could help you but it really is legal advice you need.