I just wanted to update my progress with Yoshi's marking problem. He's stopped marking in the house! Yay! Since my last post, I started correcting him when I saw him lift his leg inside the house. I also scrubbed everything down & purchased some plywood boards from Home Depot. I covered the boards with disposable potty pads & leaned them up against the baseboards where I knew he liked to mark. I started praising him for marking when we were OUTSIDE. Incredibly, the pad wrapped plywood has remained dry! However, I did all of that at the same time winter started turning to spring. Since the weather has been warmer, we've been outside a lot more. I'm thinking that Yoshi was sick of being stuck inside the house all winter long & that may have had a lot to do with his marking. Or maybe it's a combination of both. I do see him marking a lot on walks & when we play in the backyard. I also change our walk route a few times a week so he has the opportunity to smell new smells.
Here's the weird thing...now my GIRL has started marking

She only marks outside during walks, not in the backyard during play time & not inside. Is she just copying her big brother? Or do girls really mark? So bizarre! After she does it, Yoshi marks right on top of her mark!
Anyway, thanks for all of your advice! I'm really relieved I didn't have to resort to re-crate training. That would have been tough on me, emotionally. And when winter comes back, I'll make it a priority to let him have his outdoor time