The runt of the litter.?

As a follow up of my previous kitten i need some more help. i started feeding him formula with an eye dropper and as far as i know he is getting full. so i need to know if there are anymore complications of him being the runt. i keep him warm i snuggle with him and when i return him to his mom they do cuddle. so i need to know 2 things. 1 is he gonna live since we've been takin care of him and 2 are there any other things i need to know. i know about stimulating his and everything i just need to know if need to do anything else?