I think hitting F5 and using the arrow keys in-game should allow you to decrease the size of the gameplay window to try to increase performance. You might try that if you haven't already...
Yes, specifically IBM PCjr-ish clone. Compared to IBM PC 5150 it has 2x slower access to the first 96K of RAM due to “integrated” nature of its non-standard take on CGA. But, the rest of RAM is actually faster than IBM PC because it is a modern retro computing extension card made with fast SRAM.
It has TTL RGBI and composite NTSC outputs. The latter is actually very interesting in that it can produce 16-color images using color smearing effect on NTSC TV. Many games from the period used this to achieve more colorful graphics at the expense of dropping to 160x200 resolution. OP port of Wolf3d is also supporting this mode.
I am working on FPGA-based converter to be able to show RGBI and composite CGA on modern VGA screens.