He is very very young...I would say about 4 weeks now, so he was 3 weeks a week ago
Waaaay too young to be away from mom.
Where did you get him from? Do you have any other babies his age and how are they doing? You said you removed him from the other rats. If this was to prevent infection, there's no point, they have all been exposed to whatever is wrong with him. I would advise putting him back in as they are social colony animals and will stress out on their own (and get sickers).
You also will want to get him off that pine especially if its a URI (upper respiratory infection) like I suspect. Pine is actually damaging to little animals lungs and organs.
So here are my questions;
1) Where did you get him, and how long ago?
2) Is he lethargic, fur puffed up, eyes half closed, breathing hard or making noises when breathing?
3) Is he still eating and drinking?
4) Did his behavior change right after the fall? Most babies bounce like rubber when they fall, because they try insane things that make their humans run to catch them!