I would keep trying to get him on a 4 hour routine. It needs to be done and since you've gotten your feet wet, keep at it. 2 hours feed/awake and 2 hour naps.
To get past the 45 minute naps, try going into the room after 35 minutes of sleep and jostling him so he is semi conscious and then leaving the room. This will break him of the habit he has developed for sleep. It should only take 3-4 days of this at each nap to break the 45 minute naps. I just helped another Mom do this for her 7 month old!
It teaches them to put themselves back to sleep before the FULLY wake up from the nap.
Good luck and keep up the great work! My DS is 7 months old now and sleeps great at night and during the day.
Keep us posted!