The commands to raise and lower the hover height are L-Alt-J and L-Alt-K, I don't know what R-Alt-J is supposed to do.
Same with Ctrl-H. That's a new one on me, some kind of a grid display. Stable-Hover is L-Shft-H.
Some command event handling is in the dynamics section, the flying commands, but the rest are in other sections of the code I haven't dug around in. The grid display is probably in avionics, but Ctrl-H I wouldn't know where to look.

I don't know about the fps impact, I haven't compiled the code with specific settings. When you place the test.exe next to the cohokum.exe it should use all the same settings files as you've used before, I'm not sure what would be different.