Hi,
I have good experience with headsets (I use a Shure WH20XLR not wireless).
If the audience is wondering, I can say "thousands of pilots and millions of telephonists can't be wrong".
About PSR 2000 mic setting. Try to eliminate feedback. First midboost, you tune the mid frequency, when you notice feedback, stop and cut (6 to 10 dB). Reduce Hi EQ a little and bass a little more.
Use compressor and gate if available (I have the 9000 pro).
About VH, depending to the kind of song, in case of high tuned songs (tenor) I would try something like "Men Choir" in case of low tuned, I would use settings with backing voices above, like women choir, CountryX etc.
Record your voice, play it back to the mic in (line position) and check all kinds of vocalist presets.
The only way to manage multiple mics with a PSR is a small mixer. Connect it with aux in, not mic in. If you don't have aux in, connect the PSR to the mixer line in.
For PSR control, a piano-like Roland/ Technics or Yamaha pedal will give maximum comfort, but a cheap switch is ok. too. Your feet may decide.
I don't think PSR's own amp/speakers is enough for a 40/50 people audience?
I used the build in PSR 8000 speakers for 30 old people but did insert a compressor (Alesis nanocompressor).
You may use a PA system. Easy to handle and easy to transport, the HK Audio XT. Very small, sounds very large, easy to transport, sounds like a good studio monitor speaker, no mid cut like cheap HiFi speaker, no mid boost like the usual PA systems.
I used the Thomann cases for a while. They are well but heavy (keyboard plus case 30 kg), therefore I changed to bags. It's cheaper too.
It's not easy to find the best answer to you, because we don't know where you are from.
A good global advice. Use the SPL vitalizer jack, makes a bad sound good and a good sound better. Go to your musicstore and ask for demonstration.
For sheet stands, use a professional sheet stand for orchestras, it's not cheap but reliable and able to hold a LARGE fake book with 1000 songs.