Durham Physics department is really good. I've known lots of physicists who really enjoy(ed) it. KCL is more known for humanities/social sciences than pure sciences (particularly history, or at least that is the impression from someone who hasn't studied there) but ultimately I think it's a good idea to look at the course pages for both and closely look at the modules and see which you prefer on that basis.

Typical student stuff really minus the cooking equipment as your son will be catered. A bed is provided (check with Chad's via their website for specifics) but I would also bring:
- own sheets, duvet and pillows if possible
- Clothes
- books
- electronic items (make sure you have a converter/has right voltage if international)
- sturdy backpack
- a printer can be useful though not essential
- rolling bag for laundry (this was really handy for me lol as our laundry was down a hill)
- toiletries
- any required books, a folder with paper, pencil case
- documentation eg passport for registration and setting up a bank account if not already done
You can also google some websites 'what should i pack for uni' for more tips.
sorry to hear about your experience

although Durham is a great place for a lot of people, I would agree there are some aspects that are difficult especially for those that are from a working class background, disabled students, BME students or who struggle with finances. the university does what it can but unfortunately it is my belief they could do more for instance by investing more in financial support than in increasing student numbers at the expense of student welfare.
you can't get a refund from choosing to go to university unless your university is revealed as fake/fraudulent/non-existent which is not the case with Durham as it's accredited. if you do have a complaint, you can always contact the students union or the vice-chancellor if you're feeling brave although you may not receive a response. if it turns out you have a genuine grievance or feel you were discriminated against you may be able to receive some compensation although I would not count on this as this is difficult to prove.
genuine discrimination however is different from feeling let down by an experience or less-than-expected career prospects. in that case, it would be good to place some distance and not be reminded and to try to move to the next stage of life.