It definitely sounds like a LOT of changes for little one all at once! Toddlers often have trouble adjusting just from travel alone! Then you add in not only a bed change but a ROOM change, nap schedule change AND baby on the way (he definitely notices your big belly and realizes something is up, even if he doesn't know exactly how the changes will occur!
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Since you've already made the room and bed switch, there's nothing to do but stay with it. However, it's important to really talk over the changes with him (even as little as he is) and do some fun things like have him color pictures -- or you color pictures -- that you hang in his room, buy a 'special' stuffed animal that only big boys can have, find fun sheets or pillowcases that are only for big boys, etc. Make him PART of the change. Let him pick out some of these new things for his room.
As for the nap change, you're going about it in a difficult way but understand you're sort of limited due to him not wanting to take PM nap. Usually what we do is keep PM nap the longest nap and just slowly shorten AM nap while we also move it later in the day. That way we ensure that child isn't overtired at bedtime, which often leads to sleep troubles.
If he's sleeping thru the night but is simply grumpy, I guess I would worry about it too much. But 1 hour nap for the whole day is quite short when he's used to 3 hours!
I think I might be tempted to move nap later, to noon, and then move bedtime a tad later as well -- to maybe 6:30 -- and see how that goes. If it severely backfires with a shorty nap, then I guess you'll have to procede with your plan. Alternatively, I think I might still keep offering a PM nap and see if after getting used to his room a little bit if he won't go off for nap. Perhaps you could even lay down with him initially to help him along. If you only do that 2-3 times it won't be in dnager of becoming a prop.
This is always a hard transition, from crib to BBB when baby is on the way! So, you're not alone in having lots of changes to put LO thru at once. I do think in 2 months times a lot of these issues will be solved. However, don't be too shocked if DS#1 regresses a bit once baby appears. It's a lot for a little guy to take in!
