Can you display the frequency on a log scale? That is much more useful. I expect a lot of stuff in the 200 to 350 Hz region. A big room is good, or if you find specific frequencies that are really pronounced, you may end up needing a damped resonator approach to tame those frequencies.
The 'other' (not so good) approach is to close mic (really close), so you get absolutely no room, then apply enough artificial reverb to make it sound more real - or maybe bigger than real so it really hides the room sound. It's not ideal but it can work in a pinch - provided that the room doesn't resonate in the song you are recording.
Do you have a computer monitor running anywhere near your gear? Anything over 20 kHz is likely noise from switching power supplies, computer monitors, or stuff like that - provided that you are recording to 96k. At 48k (or 44.1) you should see nothing about 22 or 24 kHz.