You might be better served asking your questions about sex and orientation on this thread to get a more diverse picture, but I will answer what I can from my perspective. I’d use gay instead of homosexual, it is the more common term today and what most gay guys in my neck of the woods use when referring to ourselves. Yes, gay men are men, despite the societal efforts of the past to claim we’re not. So gay male is very much male.
There have also always been transgender individuals and while surgical options were far more limited in the past. While the earliest surviving official mention of mastectomy for example dated from the sixth century AD, there’s some speculation that it was known and used as early as ancient Egypt. Trans guys in ancient times could certainly have used other tactics as breast binding. I know less about trans women, but you could certainly ask in one of the other threads around here for input from the trans people here on this forum.
If it should really be necessary we could always make sure that our dear nemesis is accused and tried for a crime. Preferably one he’s actually committed, as Kraterous does not seem to be the most law-abiding of guys, meaning the loss of nearly all his money and possessions might suddenly, finally render himself vulnerable to prosecution.
Needless to say a proper conviction would take the decision out of his hands. If it is really necessary my mc isn’t against manufacturing something on him as a last resort.
Oh, yes, that’s one of the reasons my mc wants him enslaved into his new household. Forced to take on the (Latinized) name of a former street rat, simply delicious. 
Well if we get the good kind of manumission and have some money from our arena days, plus like all such freedmen the patronage of our former master Roman society would view us as middle-class at the very least. The only thing standing in the way of manumitted gladiators really extending their fame and fortune after they survived their gladiator careers was the rotten type of manumission they historically got. Some of the Roman volunteers, should they survive their terms as gladiators, presumably used their newfound fame and money to build all sorts of legacies.
So in conclusion my mc would post-manumission likely not be viewed as lower-class by Roman society, and how Greek society continues to view him is not something he’d care about anyway.