My partners family is effecting my relationship with myself and my partner.
In any relationship it is important that each understands the other -at least some of the time:) I'm sure your partner will understand if you do not spend 50% of the time between his family and yours. It is only natural to want to spend less time in a hostile and judgemental environment. This is not your doing, it is theirs.
Unless you wish to devote your life to seeing to their needs now would seem a pretty good time to start to withdraw. I would not be surprise if this draws further friction, but I'd think the alternative - staying on and doing so much permanently without thanks - would be much worse.
Planning on uni and having a firm idea of what you would like to do in life is really excellent, and in fact I think many would envy your sense of purpose.
In the long term having an occupation you enjoy and feel is worthwhile can only help you and your partner. It is not selfish to look after yourself and make this come about. It is dealing properly with life.
I hope you manage to sort it out and it brings you and your partner closer