rescued a rat from snake

so about a week ago i visited my sister and saw that she was trying to feed her snake a rat that was much to large. she had knocked out the rat by hitting it on the head with a ruler. he was out for about 4 hours before coming to.... (poor thing) i took the rat home and fed it and gave it water.

he was pretty tipsy for the first few days, but he seems to be fine and functioning now. he is gray and white and about 5 inches long (not including tail). im pretty sure he is a young dumbo rat, but im not sure.

as of right now im feeding him and interacting with him daily, but he is still very skittish. he constantly poops and pees when i pick him up, and when i let him run around my bathroom he poops everywhere. he never bites though, he just seems scared.
im wondering if anyone has ever experienced this type of situation before, and if so can i expect him to warm up to me? ???

also, would it be beneficial to him to get him a cage mate/ friend??

oh and, can anyone verify if he is a dumbo rat, and if so, will he get any larger.
I've owned one dumbo before, but it was about 3 years ago, and have forgotten most things.

unfortunately this is the best picture i could get of him...