Update on Oscar the Yardcat

Since his surgery a couple of weeks ago, Oscar the Yardcat has become Oscar the Library Closetcat. We started keeping him in the library because it was warm and secure, we could keep him away from the stairs in his immediate postop period, and the other cats could be prevented from picking on him. Once he got stronger, we allowed some feline interaction, but it has not gone well. Oscar is all of 10 pounds, despite having been an unaltered tom, and our big bruiser Longshanks is at least 15 pounds. And he's pissed off, so Oscar has been keeping to himself, holed up in the back of the library closet behind a heavy-duty camera case my husband keeps in there. Every once in a while, Longshanks gets a whisker bent and goes in there to pick a fight. I'm not sure this is ever going to get better.