ujm, thanks for the (self) reference.
I am looking again at the reference to YD without even mentioning Shach there. I am very perturbed when someone quotes sources “from his side”. Especially when trying to defend Torah learning. This is self-defeating.
R Moshe’s psak there is the most relevant in terms of time period. But look at his argument – you do not need college education for parnosa if you don’t want Cadillac. This was true at his time – when I think 10% of men went to college and even less of women. This is different now. Majority goes to college (obviously it is not same level as it was then) – and thus to live like an average person, you may need college. But this is off-topic as we are discussing learning non-Jewish subjects per se, not for parnosa.