Mei - of course, it is your choice, but a decent lawyer, specialising in Employment Law cost me £450 an hour, + VAT of course, 10 years ago. My bill went into many thousands. Lawyers can read very slowly, it seems.
The process was extremely stressful, and right now, you have the opportunity to walk away from a situation you have not enjoyed, into a potentially more settled role, with different opportunities going with it.
You have a lot of things going on in your life at the moment. In your shoes, I'd go for building positivity for myself, and not lingering with the past.
There is an argument to suggest going for the settled life and keep your hard earned money in your bank account.
I do know, looking back at my own position, which eventually came good, if it were to recur, I would deal with it very differently.
Of course, these are your personal decisions to make, but do consider the time, effort and emotional turmoil you could be bringing upon yourself, whilst trying to settle into a new job, pick up the threads to get back to finish your degree, as well as just getting busy living.