Since he's 13.5 months we KNOW he won't die from hunger.
So, I think what I'd do is not feed him for NWs or EWs -- wait until an appropriate waking time (6 or 7 am, whatever your family typically does) and THEN give him breakfast. This may mean 1 or 2 tough nights where he wants to feed like normal. But the result will be a VERY hungry toddler in the morning. That should help you get the nutrition in him during the day, rather than night. As long as you continue feeding at night he will want to eat then! See what I mean? With a very young baby we wouldn't do this because it's so very important for them to have regular feeds, for dehydration purposes as well as nutrition. But this is a toddler and going 12-14 hours between feeds is just fine. Heck, toddlers can go 24 hours without food without really doing any damage. And some do when on food jags!
So, just decide not to feed at night any mroe and that will get your feeds more concentrated during the day. You can even do the old bandaids on your nipples at night and say "mama's boobies are broken tonight. No more milk. Let's go to sleep."
He's old enough to understand when you say you have a boo boo.
Like I said, it could be a couple of rough nights with NWs, but then he'll get the picture! And his tummy will get full during the day, and everything will go back to normal. Treat the NW as you would normally -- with WI/WO most likely. If he's still pretty clingy after being sick, I'm OK with more soothing than you'd typically do, but avoid feeding at all cost. You can sit in the rocker and cuddle for 2 hours as far as I'm concerned as long as you don't BF.
Good luck! NWs are SO much harder to deal with after a stretch of STTN, aren't they?