Gabe is like lifting a brick, but from what I read about Ragdolls, he could be part Ragdoll. (Furry ball of jello!) His muzzle is v shaped, and he's very vocal, but what short haired breeds are big bodied?

Loki is a U shaped muzzle, very quiet, light as a feather. His mom was a feral calico, and his Tom looked like a much bigger version of Gabe. He's missing the bullseye on his side to be called a full fledged ginger tabby but he has spots on his hind quarters, and stripes everywhere else.

The boys are best buds, they groom each other, play together, share food,  everything.

Is calico it's own breed or is it just a description of coloration?

My cats own my house they just permit me to live there.

Only cat lovers know the luxury of fur-coated, musical hot water bottles that never go cold."
- Susanne Millen

Are there any breeds that are not known for mousing prowess? Or is there no rhyme or reason to some cats not been keen mousers?

My cats own my house they just permit me to live there.

Only cat lovers know the luxury of fur-coated, musical hot water bottles that never go cold."
- Susanne Millen

As for mousing - it's an instinct they all have, it's not breed-related.  They do learn how from their mothers, though, and since many indoor cats have never seen a mouse, they don't teach their kittens.

Your Gabe is a ginger tabby - he's just not a "classic" tabby.  Tabbies come in three patterns:  classic, mackeral, and spotted.  Classic tabbies have the bullseye or butterfly patterns on their sides that you mentioned, mackerals have striped sides (similar to a fish skeleton), and spotted tabbies are just that - spotted!  Loki looks like a spotted tabby and I think Gabe is probably a mackeral.

My cats own my house they just permit me to live there.

Only cat lovers know the luxury of fur-coated, musical hot water bottles that never go cold."
- Susanne Millen