Hmm. I felt like I was having Deja Vu - well here is the previous thread about the F6 recording levels
Trim and Gain settings.
Hopefully this may help a bit, but also I note that some participants in the thread have F6 records, so probably worth opening up a conversation direct if you are struggling.
One thing that I think I got wrong(ish) in the previous thread is that I think that the recorder works all the time in 32bit float, so if you want a 24 or 16bit recording it converts from 32bit float in real time. I understand that the gain is optimized for 32bit float, but this may be too low for 24 or 16 bit, hence you can apply trim to correct this - but only in 16 or 24 bit recordings (trim is not applicable and will not work in 32bit float).
You say
My understanding is that these knobs can be set to work in two ways - the default is gain control prior to a recording, and faders during a recording (with the latter only changing the LR mix). The block diagram for float mode in the referenced thread, states that you can change this default to gain control prior to and during a recording. So either way I think you do have gain control! Be careful though, as I think you can monitor pre and post faders (I am not sure if this also applies to the meters). If the meters can be set to pre-faders and you have the knobs working as faders, then twiddling them during a recording will not make any difference! You would have to set monitoring to post faders. I am not sure if monitoring in float treats the dual function of the knobs (gain and faders) the same. I was thinking that pre-gain/fader monitoring may be your problem, but in this case, I wouldn't expect to see any change in levels no matter how far you turned the knob.
I am not sure what you mean here. Basically normalisation should be a process to detect the loudest element of the recording and then to apply gain to the whole recording, so that the loudest element reaches the specified value. Normalisation is not normally selective on frequency (i.e. bass, treble etc.). What software are you using?
With the free software Audactity, the menu option is Effect>Volume and Compression>Normalize. You then get a dialogue with some check boxes - The 'Remove DC offset' should be checked, the 'normalize peak amplitude to' should be checked and you should set the value to whatever you want (say -3dB), and the 'Normalise stereo channels independently' should be unchecked (but not relevant to mono in any case).
It should be OK, but try and then listen to the normalised recording. If the normalisation process has lifted the background too much, then try again with a lower value (or if you have editing software, see if you can then reduce the background noise in post - but this is not easy and you can end up with an unnatural sound if you over edit).