Gay? Don't know & frankly don't care.
I also have never read Cream of the Jest, so I can't guess about it's content. In what I have read there's nothing like the frankly anatomical excursions that we today might consider obscene. What got him in trouble was only frank reference to baldly sexual situations. For example in one of the tales, a nobleman is about to marry and part of the preparation requires that he remove from his household a couple of young "friends", one boy and one girl. Cabel wrote "touching" parting conversations for each and in each case the protagonist was in bed with his playmate. Nothing we would call especially smutty but definitely bawdier than the norm of 75-80 years ago. Plus, in Cabel's version, both apt and amusing. So adjusting your expectations might be necessary. I can't recall anything in Cabell that's naughtier than 'Candide', for instance, if that's any help.