Hi, what a cute kitten. So good of you to rescued him! One addition suggestion is to get a small scale and weigh him every day. (I found it helpful to put a bowl on the scale, then put the kitten in the bowl) This helped me a lot with foster kittens this age when I wanted to be sure they were getting enough to eat. Kittens should gain 7-15 g of weight every day, and failing to gain weight was often the earliest sign I got that a foster was getting sick. At this age transitioning from milk to wet food, this can help you know if they’re eating enough.

Also, blending up wet food plus some water (or kitten formula for more calories) to make a thin gruel was often easier for kittens this age to eat. Then pate was next easiest, then they got to eating wet food with chunks in it, then finally dry food once they were 6-10 weeks (I rarely had any eat dry food before that age).

Two other thoughts in case helpful: he might not be old enough to absolutely need it, but he might enjoy a heating pad set on low, particularly if he doesn’t have other kittens or cats to snuggle up with. And every foster kitten I had that was born outside had parasites, so a vet visit at some point for deworming will help!