Rumsfeld would totally demand scritches and love from Jacob. Even if he can only use one finger to do it (and be very careful!), the pup has declared Jacob his scritcher.
Jacob will probably be pretty surprised to find a dog the size of a wee mousie around him, either guarding the junkyard or demanding love and attention.
Sadly, in canon, at the point of the story Bobby no longer has Rumsfeld watching his junkyard, so Rumsfeld won’t be around. (Though that doesn’t stop us from imagining him around!)