Do you know this first hand? I spoke with R' Belsky and he told me beshem R' Moshe that bal nefesh is not that high and that we should all consider ourselves bal nefesh. He also told me that he doesn't believe the stories about R' dovid and R' Reuven saying that they are not bal nefesh. Also I recently heard from someone who R' Belsky told him that these days cholov Stam is way more complicated and that R' Moshe wouldn't be matir and that the OU does it for the modern crowd...
i heard it second hand from a very reliable posek. I heard directly from reb Reuven that cholov Stam is a chumra and not din and that the Feinstein family always ate cholov stam (aside from reb Moshe)
That being said i did
see,not just hear about, a letter from reb Moshe discussing his psak to someone (could have been a journal or something) saying that anyone who is able to should try very hard to keep cholov Yisroel. I don't remember the exact lashon. Not merely baalei nefesh. Which would mean even us regular people.
After all this Rav belsky was my posek so I don't eat cholov stam and also try not to give cholov stam formula to infants as he held very strongly to try not to. Even with the heter of powdered milk.
And it is surely true that he believed that any bnei Torah (not just learning people but anyone who follows Halacha strongly) should consider himself Baal nefesh. But that was Rav belsky. Not reb reuven.
As far as the last thing you mentioned I'm not sure that is true. If you are referring to the treifos shaila involved with the dairy cows of non cholov Yisroel farms, he actually held very strongly that there is no shaila and it is mutar lechatchila. I heard it from him many times and it's printed in his Sefer.
I've never heard anything like what you said and I certainly doubt the validity. But hey who knows.