Early to bed is always your best friend, especially if naps have been less than stellar during the day.
He is almost 5mths....he should be nearing 2hrs A time.....
do you think he is capable of staying up a bit longer???
If you think he might be able to, increasing his A time should result in longer naps.
In general though, yes, i think you have a good handle on things. Don't worry about him feeding every 3.5 hrs, is he breastfed?? That's normal......
Hope the rest of day isn't too bad
sami