My 21 month old has just been through exactly this, almost to the minute in terms of WU, nap and BT. We were getting lots of battles at naptime and bedtime too.
For us, I think she was UT as we found that the next step was that she started reducing her nap length as well. Previously I'd been reacting by putting her to bed later after a long nap and earlier after a short nap but one day (after lots of help and reading on this site) we tried a later bedtime even on a 45 minute nap. We also pushed her nap back to 12.30 and then 1pm. There was no change on the first day, but we've been doing it for a few days now and this morning she slept til 6.30am with an 11 hr night!
Naps are still a bit of a problem though....
Having said all that, I know EWs can be due to being OT as well. Apart from grotty mornings, does your LO seem particularly tired during the afternoon and at night? It sounds like he could be using his nap to catch up on the lack of night sleep. Have you tried resettling in the morning? We bought a Gro Clock and I found that by using WIWO she would go back to sleep for half an hour or 45 minutes if she was still tired. If she wouldn't settle then I realised it was cos she'd just had enough sleep and eventually I could tell from the way she woke up whether to bother trying to resettle or not.
Our LO started cutting naps as well eventually so that's how we started. Have you tried waking your LO earlier from his nap? I would cut to an hour and a half initially, then maybe an hour if after a few days it's not helping, and keep bedtime to around 7ish for now. We're now on:
WU @ 6ish (variable - started at 5.30 am, gradually moving back to 6.30am)
Nap @ 1pm for 45 mins
BT @ 7.30 (and straight to sleep! Yay!)
The other approach I've seen on here is to allow a long, late nap and then do a super late night in the hope it shifts the next day later as well, but we couldn't try this in the end as Lily started cutting her naps herself!
