If you got him as an 8 week old weaner in March, he'll be almost 10 months old by now - you'll need to watch your gilts carefully as he may have already got to them
and don't think his small size will stop him
The taint issue is a very subjective one - not everyone can detect it. 1 in 4 woman and only 1 in 7 men can smell it, so it might not be an issue for you at all.
I'd take a girth measurement and length measurement and calculate how much he actually weighs - small pigs are just as tasty
Though obviously if you're paying a set butchery fee per pig you want to get your monies' worth.
If it was me, I'd send him with the rest because if he did stay the chances of him impregnating his sisters is an almost certainty (whispers.... which I why I castrate my boars)
HTH
Karen