Mr. Cat is an absolute bastard of a fight. As with everything else in his dungeon, he only attacks once every two turns, but he can use any of the moves from the enemies in there. And as you've no doubt noticed, past a certain amount of HP he decides that he gets to ignore that drawback. I would recommend slow-playing your resources until that point, and then swinging for the fences with everything you've got.
I don't think you presently have anywhere that sells better gear than Shinryu? You're right that the Arena and Dark Dungeon have good alternatives though, ESPECIALLY if you manage to get the rare treasures hidden in every five-floor range.
I don't think you presently have anywhere that sells better gear than Shinryu? You're right that the Arena and Dark Dungeon have good alternatives though, ESPECIALLY if you manage to get the rare treasures hidden in every five-floor range.