{{{{{{hugs}}}}} - sadly, yes, he will practice all his skills there in his cot.....but that is very normal. I would give him loads and loads of opportunity to practice during his normal A time, so it's less appealing at naptime. Generally, we recommend doing just pd when they start standing - you'd lay him down, say your sleepy time phrase and leave the room. Well done on pu/pd and GW - since you're already almost out of the room, I would not go back to being next to his bed. When you lay him down, go ahead and leave, then if he stands up and is crying for you, then come in and do pd, and leave. You could just leave to your spot by the door initially, that would be fine.
If he stands up and is not crying for you, I would not intervene - give him the chance to figure it out and settle himself. When/if he starts crying, do pd, resume your usual place. I would keep your interaction as minimal as possible "lay down...it's time to sleep" and say the same thing each time.
Usually, you have to just ride things out and try to avoid creating another prop in the meantime (which is why I would not regress with your GW - you've worked sooooo hard, you don't want to go back). Hang in there!
hth
michelle