Re: Likely silly, but advice?
He does look a bit on the heavy side, I I compare to mine. In any case I would visit the vet because those loose stool doesn't sound good. Make sure he stay hydrated, I was once told to suplement with some clear Pedialyte.
As for the grumpy side... maybe thats just like that. Litchi is quite unfriendly, I manage to do her nail but that's a nightmare and I get bit everytime.