One Nap Transition Help

My 13m (14m next week) just started one nap a day on Monday- around 12:30/1. Here's the issue - we're back to half hour naps where he's screaming waking up and miserable (fussy/needy)for an hour thereafter. Before one nap transition he napped at 9:30/10 for an hour and was consistently refusing second nap. Both naps and bedtime he would fight - cry hard and I'd have to go in and console every few minutes for 5-15 minutes. With one nap he falls asleep immediately at nap and bed- eyes are fluttering shut during stories. With the exception of last night he started to sleep better at night.

Bedtime 7/7:30 wakeup 6/6:30. Bedtime has to stay that time based on big sister schedule. Naps have to be either 9:30/10 and 2:30/3 or 12:30/1. I can't do a slow transition since we have activities around 11 (and 4:30).

Will the one nap get better or should I leave it two and deal with the fights?