Hi there
Can I ask a few questions which might help us to understand the situation a bit better? Firstly, please could you post the whole day's routine (or an example day - pick an actual day rather than an average), eg:
WU 6am but chatting in cot until getting up 7am
E 7am
S 8:30-11
E 11am
S 1-1:45 (any resettling attempts etc?)
... Or however it is for you
Secondly - could you tell us a bit about how he's settling for sleep and where he naps? How much help do you give him, for example? Are you out and about or at home in the cot? Swaddled?
I didn't quite understand what you said about night feeds - sometimes he drinks 4.5oz twice in the night, and sometimes nothing at all, or did you mean not all of the 4.5 oz offered?
Tbh it's quite usual for a 4.5mo to still be feeding twice in the night, especially considering that there's a growth spurt around 4mo. On the nights where he feeds well and goes straight back to sleep, I'd consider that normal, he'll grow out of it eventually but probably just needs the milk then for now. On nights where he doesn't want milk but is awake for some time, what does that look like? Is he crying/babbling/fussing/squirming/gassy? What do you do to settle him when he wakes?
Regarding the long morning nap, in general the advice is not to let them sleep more than 2h at this age, or it can backfire later on - just a rule of thumb of course, but it seems to work for many LOs.