Yeah, he does look skinny. Maybe the back to back large rats were to big of a meal with too low of temps. His injuries look like they might of come from him being stuck behind a decoration and ripping himself trying to get out (it looks like its running a line down his side to me). Neosporin will help, so would a betadine rinse. If it is from that, it should heal (poss. scarring) with proper treatment.

But with his loosing weight, you might want to double check your set up and get a fecal done, just in case. Lots of stress can keep them from eating. Also try offering him a live wealing/ small rat or mouse... he may have decided that large rats are too big for him now.