Hmm, unless I am missing something, it looks like a pretty good routine! 2 hrs A time is quite long for 3 months old, it's usually more like 1.5hr - but if he is napping well on that then myabe your little man is OK on longer A times... so you have 3 x 1.5hr naps but no catnap, is that right?
Has he always been on 4-hourly feeding? Again most don't move to 4 hourly until nearer 4 months but again if he's been on that for a while and been OK...
Think there is a growth spurt around 3 months so it "could" be hunger - but you would only be looking to feed him once during the night in that case, not every 2 hrs.
So could be the dummy... everyone does half wake up in the night but then just go back to sleep so it is important that he can get to sleep independently. does he usually go to sleep independently at the start of the night?
Could he be teething?
I am sure you are exhuasted - it's no fun... let's see if anyone else has any ideas!
Bryony