What humidity and temp. range is recommended immediately after repotting to s/h?
 

I know warm, shady, and humid is recommended while establishing new roots in s/h. What ranges are we talking? My room temp. right now is 77 with humidity around 76% to 80% I just finished repotting so I do not have a full range (high/low - day/night) for the room. I will try to update tomorrow. A seedling heat mat will arrive on Monday, hopefully. (Plants switched so far: Oncidium Sherry Baby, Maxillaria Tenufolia, Phrag. Laura Lei Quintal, Phal. Kaoda Twinkle, Pot. Mem. Jim Nickou 'James' HCC/AOS x Blc. Love Sound 'Dogashima' AM/AOS, & Masdevallia 'Peach Allure').

Next question: My Masdevallia 'Peach Allure' was also put into s/h. It was previously grown in a bark mix sitting in a tray of water. My question is : Do I put it in the warmer/more humid room to establish or just put it back where it was happily growing since it was already growing in a s/h way, just in bark instead of PrimeAgra?

I can't help with the Peach Allure. But your temperature and humidity should be fine for the rest.

By far, the most important thing about moving to S/H is making sure the plants are actively growing new roots at the time you move them.

All had green root tips, except one Phal.. It was failing rapidly in its previous pot. This was a last ditch effort to save it. If it doesn't make it, I at least tried. It wasn't going to make it where it was. I have saved them without roots before, hopefully this will happen again. The modified room is a much warmer/humid environment for it than its winter home was, so fingers crossed.

The concept behind maximizing the humidity is to reduce the desiccation stress on the plants while they grow new roots that will enable them take up water. All transplants can benefit from that, but especially plants like your phal with no roots.

I usually recommend inverting a clear plastic bag over the plant and pot to trap the humidity.

Actually, I did that with a Zygo.. From transplanting yesterday to this morning it has developed fuzzy mold on the new growth. Any suggestion on preventing/treating the mold?

Mold won't grow on healthy tissue, so if there's mold, you've left some necrotic tissue exposed.