You're right -- it does look like he may have gained. His diet hasn't changed... I'm inclined to think it may partly be that his winter coat is just fluffing out. He's super plush to the touch since I don't blanket him, and his coat usually keeps filling out well into January. If he's still looking this well fed in February I may start to pare back his diet a smidge so the spring bounty doesn't make him balloon too much.
Thanks for all of the input. I'll look into getting some of these other things addressed. His feet sure are tricky though.