Pot size after cutting dead roots?

[DesignerofBeauty]

Hello All,

I'm a bit nervous right now, and I have a few questions:

The first being, how do I deal with mold? I am repotting all my cattleya orchids at the moment. I noticed that one of my orchids (which I haven't repotted since I bought it) had mold on some of the medium and a ton of dead roots. The mold was definitely not mealy worms. It had the white web-like texture to it. There was no mold on the roots (at least the ones that were alive), thankfully. I had to cut all the dead roots. I'm afraid it won't revive, but I'm going to try my hardest. I plan on pouring 3% hydrogen peroxide on it and letting it sit out of the medium for a week.

The second question being ... Since I cut down so much of the roots, I'll have to put it into a new pot. I'm not sure if it's the right size, and was hoping you guys could help me with that too. This orchid's pot is the orange pot that is pictured. A new orchid that I just purchased needs to be upgraded to a bigger pot (it's original pot is the green one pictured). I was thinking of switching the orchid's pots (after pouring bleach on both pots of course). Are both pot sizes appropriate?

Sorry for all the questions I've been posting lately! I appreciate all your help.

Thanks in advance!