No snacks.
Maybe it’s just his little way of coming out to the rest of the family? Just let him know that while you’re supportive of his lifestyle, you don’t bat for that team – not that there’s anything wrong with that.
“Queer.”
In other words, what legalsnugs said? 
“I don’t want that caught in my teeth!”
“I would if I could find it!”
StG
I like this one.
“No thanks, I would prefer not to suck your dick.” I wouldn’t worry about being vulgar in front of his son; he apparently isn’t.
Say “Wow you and your wife are so demanding today”
Yeah, but cruder and without all that chit chat.
Sure, your wife keeps it in her purse, I’ll go get it.
So insulting his religion is okay, but insulting his penis is off the table. Just checking. 
I’d use a much more offensive pejorative along the lines of what MeanOldLady said.
And Cat Whisperer, I can tell you don’t have much experience with male banter of this sort. OP, don’t say what she suggested. 
“Sorry, Dude. I choke on small bones.”
You have to buy me jewelry, first.
And as he writhes in pain to hide his blade job, you get your heat by doing crotch chops while standing on the turnbuckle.
“Okay” Proceed to pretend to make a motion to fellate him. Either he will recoil away OR it will get you close enough to proceed with Phase two of your plan:
Phase Two: Loudly proclaim “Nut check!” and follow it up with the aforementioned nut check (a flick of the wrist/quick jab to the nuts).
For added meanness, teach his son the art of the nut check, and try to see if you can get the son to give his old man a shot to the nuts as well.
Beware- employing this tactic is like using a nuke- once you’ve launched it, there’s no going back to friendly grounds after this- both of you will live in fear of the nut check, and both of you will have to constantly be on your guard- for both of you are males, and have the same weakness, and he WILL want revenge… they always do. But consider it your end game plan, if you can’t take it anymore, just go for the nut check, and try to protect yourself from that day forwards, because revenge will be coming… Hence the added bonus goal of trying to teach his son to try to do it- make the old man live in fear of his own offspring!
“Give me a magnifying glass and I’ll see if I can find it first.”
“Okay, but you’ll have to demonstrate first.”
I don’t remember this exactly, but here goes:
<Rocky Horror Sing-Song Chant>
Incest is best! Put your sister to the test!
</RHSSC>