it looks to me that he was quite the champ sleeper before this strike!!!! maybe he still needs his nap to be long. I'd try, instead of limiting the nap to 1.5 hrs, maybe just put him down later, say 1230 - 1245 (if he wakes at
and limit the nap to be 2-2.15 hours long. That should be enough for him to get the rest he needs in the midday but also prevents him for being overtired at night. Since you say he goes down easy for naps and gets super fussy for bedtime, it looks like he might be overtired then. If he wakes from his nap at 230-245 instead of the 130 that you say you're waking him, he might go down easy then.
You mentioned he's having seasonal allergies, which can also lead us to think about lactose intolerance... worth a visit to the ped so he can give you some light on that insight. You can also try posting in the Health/Medical advice forum for info on this. Because yes, if he's having an upset tummy at night, I know first hand (having tacos for dinner for example LOL) that it can prevent you from going down easily...
Good luck this weekend!