Jim,
I suspect I've run out of different ways to answer. You seem confident you already know what's out there, and all 'findings' from data are only interpretations after all, so if you're really not willing to change your own view why ask? I really don't 'know' what's out there, and do change my opinion, which is why I study a score of new papers a week to keep up with findings and form the most consistent view. Is that not how it should be done?
I'll try not to be 'belittling', but when you don't seem to see the clear conclusions from the descriptions I'm sorry, but I could only assume you were making some wrong assumptions. Shall I try with just some simple one liners;
Because it is significantly ions, which don't 'emit' radiation unless being charged.
Ions also don't change the received charge signal so are largely 'invisible'.
We CAN and DO see bound molecular gas, where 'hot', at various wavelengths.
Most gas is too 'small', diffuse & cool to 'see' at 100mm let alone 100 light years!
Poor instrumentation. We see much more now, and will see much more in a few years.
Did you not 'see' the clear oblate spheroid halo of Centaurus A in my photo??! Please also explain if you don't agree with or accept the 5 points above.
I did explain about X rays (delta lambda) if you look back, but will do so again; Excitation (coupling charge) does it, as does rapid motion towards the sensor. It may be emitted at UV, but if the gas is approaching us and we are approaching the gas (on our orbit) it is scattered (Stokes 'up' or blue shifted) to X-ray. I did previously explain that's how we ascertain the rotational velocity of galaxies.
If you wish to actually 'see' the most dense and energetic bits we CAN detect directly perhaps Google; 'galaxy halo shape images'. A very good short summary of a recent finding is here, but from behavioural not 'visible' evidence. Nevertheless it certainly can't just be dismissed; Beachball.
Going on the full range of observational evidence I find one interpretation overwhelmingly consistent compared to all others. Like yours it is not quite the Concordance model, but it resolves the problems within that. Are you sure you are not distorting your conclusions by discarding the vast majority of 'observation' just because it's not 'direct'?
Peter