The only advice I can give is PLEASE PLEASE PLEASE be very careful about feeding and keeping him warm, etc. Baby birds are very fragile and VERY prone to stress, so keep him in a QUIET place away from any animals and a no-traffic area of your house, such as a bedroom closet.

I recently found a baby bird, much older than the one you have appears, and he was doing fine... but just very suddenly passed away without any warning. He was eating and drinking fine, too, so I'm not sure what happened. The morning that he died actually he was so active, he was hopping out of his box and trying to fly around our closet!!! So I'm not sure, they are just so peculiar so please take extra caution and care!

There are a few bird forums I found when I had my bird via googling, perhaps you can join one of those to ask questions? They may be much more knowledgeable in IDing him and giving you tips on how/what to feed, etc.

GOOD LUCK!!!!!!!!!!