This problem seems to be a legacy one. I added the touchscreen later when everything was up and running. Changing the resolution was done via editing the options.lua because I run a 3x1 + 1 setup, so the desired resolution doesn't show up in the dropdown in the options menu and I didn't know back then that I could simply type in the resolution.
If done via the options menu, the new aspect ratio for the overall sim is automatically recalculated, but not so if the resolution is set via the config files. I didn't change it from the 5.6 I had because I figured this number only affects the 3D portion of the rendering system. Boy was I wrong.
The aspect ratio of the 3D view is set in the monitor lua. And if you don't have the right aspect ratio set in the options.lua, all coordinates and size parameters in the monitor definition lua seem to be interpreted wrong.
If your overall res is what you stated, the calculated aspect ratio is to be set in the options.lua in your home directory (saved games in your files, DCS folder). In the monitor definition lua, the aspect ratio has to be set accordingly to the 3D output, i.e. you subtract the vertical resolution of your touchscreen from the overall res and do the same calculation again.
7968 - 1920 = 6048 -> 6048 / 1200 = 5.04.
So the aspect ratio in your monitor lua for the main viewport has to be 5.04. If done so, all the coordinates and sizes for the indicators will behave correctly and you don't have to position and resize every gauge by tedious trial & error.