I have a mxt575 with swr of 1.54 and power output of 48.8 watts.
That's using the midland antenna that came with the radio mounted on a sr offroad a pillar mount with the ditch light.
I tried the magnet mount on the rollbar and got a 1.01 swr.
Also, if you weren't already, check your output...
It is strange. A switched source is a switched source. Shouldn't matter if it's a power point, toggle switch, or aux switch that is controlled by the position of the ignition switch.
Just for fun, run a temporary power circuit to the battery with a toggle switch and see if it works. Shouldn't...
The glovebox is open to the top, so there should be more airflow with the dash cavity getting air in from the front floorboards.
When I replaced my dash speakers, I could see down into the glovebox from the passenger side speaker location.
That is a very nice radio which I plan to eventually get.
If it does fit in the center console under the cup holders, I would be concerned about airflow, especially when transmitting. That particular radio has a cooling fan that may help a little in an enclosed area, but it does produce a good...