Try the -cga flag.
That would fix it if it's mis-detecting MDA... but the game might just be bugged. I have only tested this on emulators. One person did have trouble with a CGA+MDA card, but that still showed buggy CGA output. In MDA mode it never writes anything to that address space.
If it's simply wrong on hardware, the source code is one file. Open Watcom takes one arcane command (see top comments in source code) and runs on anything. The problem is presumably in cga_initialize_screen, which contains some magic register operations I fully admit I do not understand. 160x100 "mode" is reasonably well-documented and this is a 40-column version of that 80-column hack.
At some point I need to update this, myself. But not today and not tomorrow.