My very first orchid was a phal that I kept in sopping moss and it had root damage. It took a long time for it to flower after that. Otherwise I don't understand it, but if watered properly that old of a plant should have a ton of healthy roots and three leaves sounds like it is growing very slowly also. For water, moss can be tricky. You want all the roots to almost dry out each time, and bark is much more forgiving. At the same time you have to bear in mind that water is what actually causes plant growth (turgor pressure), so you want to get as much of it into the plant as possible without getting rot. I mist the surface roots and external roots once a day while waiting for the middle of the pot to get some air. For light you can tell by the leaf color - a light green is what you are shooting for. If they are turning yellow that may be sunburn, and dark green is too little light. Southern windows are tricky because the direct light is too strong and the indirect light is very weak. You might want a light instead or a north eastern window works well for me. I would also cut back on the fertilizer for a while, as too much N can inhibit flowering. Hopefully it is working on a nice surprise for you after being outside!