I"m sorry - I must have gotten confused....hopefully this post makes more sense
Is there a reason you want a short am nap and a long pm nap? That is definitely one approach, and it's what I did at first. In that case, you keep that morning nap at the same A time every day (so if you've been doing 3 hrs, you could keep it at 3 hrs, that's fine), but yes, you do wake him from that nap - gradually shorten it. So if you're on 45 min now, keep that for a bit, but then you want to gradually shorten it to even < 30 min. If he's been taking longer am naps, I wouldn't immediately cut back to 45 min. I'd cut back 15 min every 5 or so days. So if he's taking 1.5 hrs, then go to 1 hr 15 min, then 1 hr, then 45 min over the course of a few weeks.
At the same time, you want to reduce the next A time - I'm not sure if you've been doing that. The reason you want to reduce that next A time is because he's had a shorter nap, so he won't be as well rested to handle the longer A time. So if his 2nd A time is 3 hr 45 min with a full am nap, as you cut 15 min off the am nap, cut 15 min off that A time as well (so bring it back to 3.5 hrs). Otherwise, you get an OT pm nap (and it sounds like that has happened).
This plan really works best for bubs who need a longer A time between their last nap and bedtime. If that tends to be your ds's longest A time of the day, the plan should work. If he does not need (or cannot handle) a longer A time before bed, this plan may not work for you. That was the case with my dd - her shortest A time is between her last nap and bedtime, so when I tried this plan, it was a complete disaster - she was too OT to take her pm nap, and then she'd only have a 45 min nap all day and that was just disaster. So if you find yourself in a situation where he is not adjusting well to this approach, you may want to switch to the other approach (long am nap, short pm nap).
In terms of early bedtime - if he's up at 6, no, I don't think a 5:30 bedtime is too early for him. Part of the struggle with the 2 to 1 switch is that EWs mean early bedtimes, which can lead to EW - but because they've already had a full night of sleep. So I wouldn't put him down before 5:30 if you can help it. Even if he sleeps 12 hrs, that's stilla 5:30 wake up.
I'm guessing the 30 min nap you got today was OT. If he refuses his first nap, I would try again in 30 min or so - rather than taking him all the way til 12:15 - it looks like that was a bit much for him.
hth
michelle