Hey K.! Hate sleep troubles, hate them. You said he managed to push his bedtime back an hour...I would take that into consideration every night and start the bedtime routine an hour earlier if you can. Or as close to an hour as you can. Also eliminate the after bathtime play like the previous poster said. Bathtime is kinda like playtime anyway in our house! I definitely wouldn't give in to the later bedtime right now because then you run the risk of letting him get overtired and I'm sure you know it's harder to get an overtired child to sleep. If he's not taking his last nap, you have to move his bedtime up anyway. Say you know he can only make it 3 hours between sleep then that's what you have to respect even if it seems unreasonable to put him to bed at 6:30.
The other thing is-if you've already had a few days of this, he's probably overtired during the day and you'll have to do whatever you have to to get him a good clip of daytime sleep. We do cry it out in our house, it's what works for us, so I understand. I don't think letting him cry for 2 hours through his nap is going to help. You would think he would wear his little self out and sleep though. Get him up after an hour, do whatever you usually do when he wakes up from a nap and try to put him down again as soon as you see his sleepy signs.
I just reread your post and understand what you're saying about 8:15. 8 isn't an unreasonable bedtime if he's getting the right amount of daytime sleep which he's not right now, right? I'm sorry this is so long, but I also just reread "Healthy Sleep Habits, Happy Child" so I'm on a roll here. :)