Welcome to the Orchid Board!
From what I can see, your plant is growing in bark chunks, and not in moss. You are correct that you should let it dry out between waterings. If it's still moist, don't water. You can spray the roots hanging out of the pot. And, if it's really still moist after 2 weeks, I would guess the pot is too large for the plant.
Most orchids sold in markets have been growing in their medium for a while, so they are due for repotting. You can repot Phals in bloom; if roots are healthy it won't affect bloom lifespan.
The yellowing leaf may have sun damage. Phalaenopsis are better in bright shade, without any direct sun, until you are an advanced grower and can judge light better.
Air roots grown in very humid environments often shrivel when moved to a drier environment, like in many homes. If the roots in the medium are fine, this is not a problem. The plant will grow more roots.
The flowers are dropping because the plant isn't taking up enough water. Because the medium is moist, I suspect, along with Roberta, most of the roots are dead. I agree with her; I would unpot the orchid and repot into fresh bark. Depending on where you live, it can be difficult to find good bark locally. You might have to go to a good, family-run nursery. The bark sold at big box home improvement stores is often really not very good.
There is an excellent thread here on Orchid Board about growing Phalaenopsis:
The Phal abuse ends here.
And there is a thread about using wooden cooking skewers to test wetness inside pots:
Using skewers to determine when to water
Often a plant that looks like yours is actually near death, so be prepared. If the roots are all dead, it is possible to reroot the plant. Don't give up quite yet.