As @Crazycrazylady said - the thread has been hijacked by some very specific viewpoints.
Those arguing the brother should give up his career are doing so on the basis that the foetus has rights to financial input and attention from the OP's brother from conception. And that he should find the best job he can locally that will support the future child from pretty much now.
That he should provide 50% of the childcare - though that would presumably not kick in from birth, since the ex-GF would presumably be breastfeeding. And presumably she will not be planning to be working or studying (based on what the OP says) for the future child's first year - so there is no specific need for childcare. Even going by the traddiest viewpoints, it's not clear why he should give up his first year at college at least. The foetus isn't born so costs don't kick in yet. And small babies don't themselves cost a lot.
Even going by their rules, he should certainly go to university for the first year at least, and then see what turns up - he could possibly transfer to second year more locally, or take a leave of absence, or whatever (though of course I don't really think that - I think the best thing is for him to get the best degree he can).
In which case, the moral demand express on this site by a minority is that he should give up his place and work and save in his home town seems to be just something punitive.
Putting it this way: say that in 10/11 years' time the OP's brother is established as a GP - he will be on about £70k. If he decides to leave Medicine early and go into finance or law instead, he could be on much more money - especially with a Cambridge degree. Even assuming his home town has plenty of good-quality work for bright people who didn't go to college - for example, in the tech industry - will he be on the same salary trajectory?
In which case - imagine you are the ex-GF in a few years' time, with a new partner, and a small child. Would you rather that the OP's brother was in a position to provide 15% of a good salary reasonably soon, or 15% of an average salary, since the option of Happy Families was just never on the table? It is absolutely the right thing for him to anticipate their change of heart and communicate that now. Separately: the future child would benefit from a higher salary, and it's absolutely in their best interests that one parent pushes their training and career forward, with a view to the future wellbeing of their children.
Children have the right to be wanted by both parents. It's very hard for children who gradually realise their parents have made extraordinarily difficult sacrifices because they were a surprise baby. It was more common in my generation to have had parents who felt obliged to do the right thing. It's not good to be aware of that sadness, often bitterness. Children do not ask to be born, so it's best for them if they are actively planned and wanted by both parents, when they have the time and resources to ensure they have a good upbringing. And adults do have responsibilities to their own fulfilment, as well as the upbringing of their children. It would be harder for the OP's brother to begin medical school at 37/37 once the eventual child has themselves become independent.
In this case, the OP's brother just does not have the time and resources to provide more than goodwill and the promise of more active involvement later on. This is not the economy or society that we live in. And that is often how parenting works within 'intact' households, where at some points one parent just cannot be very available. Why should expectations of him be so much higher than of many, many other fathers in intact households, who are studying or contributing very little in the short term?? Would people feel just as strongly about him dropping out if he were already a year, two years, three years into the degree??