Advice on 8/9 day old kitten, my first bottle baby

Just took in my first bottle baby who was estimated at ~8/9 days (he's eyes are just starting to open). I'm hoping you can help me out with some advice.

My boy had liquid diarrhea from 6:30 last night until 9:00 this morning, I think from overeating yesterday morning (he sucked down 10 ml three feedings in a row). No poops at any feeding since the 9:00 one this morning and that one was brownish and soft rather than liquid, which I think is good news!

I did take him into the Humane Society this morning and they said he doesn't seem overly dehydrated, which is good news too, and his pee has been coming out clear/light yellow. I've been using pedialyte in his formula to try to keep him hydrated and his weight has been stable at about 212-214g, but he isn't gaining like he should be.

My issue is that I can't for the life of me get him to eat more than 3 ml at a time right now. I did some research online and it says that diarrhea can inflame their stomach/intestinal lining, which makes eating more than just a few ml at a time painful and someone recommended moving from feeding every 2-3 hours (I've been at 2 hours) to every 1.5 hours during the day and go back to 2-2.5 at night.

Is this what you'd recommend or is there something else I should try?

Thank you so much for any pointers you can give!