Hello, I'm Dr. Deb.
I recently came online and see that your question about your kitten hasn't been answered. I'm so sorry that you've had to wait for a response,but if you still need assistance, I'd like to help if I can.
Typically, the kitten milk replacers indicate on the label how much you should be feeding based on the body weight of the kitten.
But, if this information isn't provided, then I recommend 60 cc's of formula per pound of body weight for the first week and 70 cc's for the second week and 85 cc's for the third week, divided into at least four equal feeding (although every three hours is fine, too).
So, if this little one is about 2 weeks of age (which makes sense since the eyes are starting to open) and weighs about 6 ounces, then I'd be feeding a about 35 ccs/day or about 9 cc's at one time (if feeding four times/day).
If you've been feeding every three hours around the clock, that means you've been feeding him 8 times in a 24 hour period, 8 x 4 = 32 cc's so you're not too far off from what I'd recommend.
So, yes, you can increase the amount being fed to him.
You may already know this, but kittens this age can't regulate their body temperatures, so be sure that he has an area where he can crawl away from the water bottle if he's getting too warm (another reason why he may be vocalizing).
I hope this helps although, again, my profuse apologies for the delayed reply. Deb