Desperate to save mature Phal orchid

[Ellzeena]

Long story short: 15 yo orchid in constant bloom, enormous and healthy, developed air roots was climbing out of pot and supplier of potting stuff gave me the worst advice in the world. Plant almost died. Has been in hospital care. Clear slotted pot, sphagnum moss (its usual medium), saw green mold so unpotted. Stem easily 7 inches long, was soft, cut in half, sprayed with hydrogen peroxide, saw thrips, sprayed with organic compound used once before many years ago, saw new root buds just starting (had to cut off yet another yellowing large leaf), repotted in sphagnum moss smaller pot; has one new leaf that is curling but not blackened. Watched Miss Orchid or someone on YT. She says do not pot but place plant in cup with sphagnum moss at bottom that is kept moist until roots begin to grow enough to pot again (and obviously do not feed). This plant means a lot to me. She wants to survive very badly. Am I doing the right thing by repotting? Did not cut stem off completely, SHOULD I? how to supply new root buds with humidity since they won't be able to absorb water? ANY HELP SO APPRECIATED.