Dear S.,
I understand your frustration about naps. I have two little girls (almost 3 years and almost 7 months) and luckily both have been phenomenal sleepers. One thing I can say for sure is that making them go to bed later is NEVER successful in getting them to sleep longer. Sleep patterns can change based on a number of issues i.e. illness, teething, growth, etc. My daughter was consistently sleeping 45 minutes for her first nap and then 1-3 hours for her second. Suddenly, she was sleeping no more than 30 minutes and it was a struggle just getting that amount. In a few days she is back to her schedule. This will happen and you just have to ride it out and keep as closely to the routine as possible.
I would also advise you to keep the 2nd nap. Nine months is still too young to only have one nap a day. Kids these days are way overtired and bad sleep habits start very young. To me it seems like the time between wake up and naps is way too long. Naps should be no later than 2.5 hours after wake up. He could be overtired and unable to sleep. Plus, that bedtime is not too early. My youngest daughter goes to bed between 6-7 every night. I followed the same pattern with my older daughter and she would sleep 11-12 hours a night. This bedtime is also dictated by her last nap and what time she wakes up. If she wakes up too early from her 2nd nap I always try to put her down for a third time so there is not a huge amount of time before she goes down for the night and is too overtired to sleep.
I swear by Healthy Sleep Habits, Happy Child written by Dr. Marc Weissbluth. He is a pediatric sleep specialist and his advice is incredibly helpful. His method has worked for us! P.S. His suggestion for the perfect bedtime is between 6-8 pm.
Good luck!