What a beautiful sch you have there! I think part of the problem may be too much sleep. I would suggest leaving naps as they are and putting him to bed a half hour later, 7:30. You want to aim for a 12 hour day and 12 hour night. Most babies 6 months take 2, 2 hour naps and a 45 min cat nap so you really aren't far from that. Does he seem ready for bed at 7:00 or could you wait a bit.
There is also a huge growth spurt at 6 months which could be causing some of the problem. Has he started to crawl or roll over recently, that also tends to effect sleep.
Hope that helps.
Myia