Need some advice on sick Phal

[estación seca]

This plant should survive with reasonable care.

I would not cut off the old stem. Others would do so.

Pot it into your usual mix. In a warm, humid climate such as yours, large bark, LECA balls intended for hydroponics or lava cinders should work well. Sphagnum moss might stay too wet until you learn how to grow with it. Have the level of the mix just above the lowest root. Some of that root will protrude from the potting mix.

Keep the plant warm. Water when the medium is almost dry. Put it someplace with high humidity, and in bright shade. Until it makes more roots, I would use a spray bottle to wet the exposed roots every day. This would only take 1 or 2 sprays.