Daas Yachid,
Although I am not so familiar with R’ Forst, it seems to me that R’ Dovid’s opinion and the fact that R’ Moshe did not publish the teshuva that you quoted is evidence enough of R’ Moshe’s true intention for a public psak. R’ Moshe might have been more machmir in different situations, depending on the circumstances, but that is clearly not what his published (by him) teshuvot imply, where he says that a baal nefesh should be machmir.