There are no "problems" with the stretching, you just don't like the Maelstrom default that is meant to be a compromise, and it is intentional.
First, the Storm 2.8 stretches all screens to full width, even widescreen, and it does not do what your screenshot 2 shows. I launched COAS, using the original cd version of Storm 2.8 with 1920x1080 and here is the result:
What you want is probably from TEHO's version, but I don't have their source code, so I'm not sure what they are doing, but I think they are constraining all screens, except for the background image, to 800x600 ratio, but I don't want to do that because it creates too much empty space for my tastes. So the Maelstrom compromises, by stretching some by default, but not the full width; I just think that looks better...apparently some people disagree. Maelstrom in 800x600:
Same screen, Maelstrom default in 1920x1080, stretches a little, but less than Storm 2.8:
If the screen's .ini config file contains noresize = 1, then it will stretch the full width, just like original Storm 2.8 did (first screenshot, above).
But apparently the small stretch greatly frustrates the Russian modders, because you are probably the 3rd modder to complain that it doesn't act like TEHO. So, in order to once again compromise, I just updated Maelstrom today and there is now a way; add resizeFactor = 1.0 to the [COMMON] section of the RESOURCE\INI\interfaces\interfaces.ini file:
[COMMON]
resizeFactor = 1.0
....
....
Hopefully this is satisfactory.