Please don't reduce his feeds! He's drinking that much because he wants that much. How is his weight? That is the ONLY sign of overfeeding. Everything else could be simply colic, silent reflux, fussy baby or something else.
Keep feeding him as you were, he doesn't need to fit into guidelines on a box.
I would suggest seeing your HV with any concerns regarding feeding, but demand feeding has always been heavily pushed where I am, and it's worked with all 3 of mine.
For what it's worth, mine fed NOTHING like the guidelines. I used to look at the box of formula in my sleep deprived days and think '4 feeds?! I'd give anything for 4 feeds a day!' But my babies wanted 6 feeds, so they got 6.
None are obese.
So please don't cut down your babies milk. The first 6 weeks are very intense and the baby is still getting used to being on the outside (look up 4th trimester). Keep doing as you are, you're doing a great job. It will only get easier.
You haven't mentioned what other symptoms of overfeeding he apparently has, but I'm sure you'll find they're similar to those of colic or intolerances, or silent reflux. It's easy to read the symptoms online and agree your child has them, but the symptoms are not exclusive.
I'll say it again as it's so important, the only real symptom of overfeeding is weight gain.