Joseph,
Part 2 of the teshuva you cite is a lengthy explanation why a man can wear a wedding ring (even though it is a goysih custom) and after permitting the practice, the Rov concludes, “perhaps, for a yireih shomayim, it is ugly to wear a wedding ring, it is still not prohibited.”
It is not clear at all if the Rov means it is ugly for a y”s to wear a wedding ring because it is what goyim do (which is the topic of the tshuva) and therefore non-wedding rings are not even ugly for men to wear or if he means all rings are ugly for y”s men to wear.
In any event, your blanket statement “it is forbidden for men to wear jewelry, has now been refuted by two sources.