The JPAC has a video amp, so you should be good in that department.
Counterintuitively, the "brightness" control doesn't actually control brightness. What it actually controls is the level at which the monitor gets "black". If you have it set too long, things that should be dark but still visible are completely black. If you have it too high, things that should be totally black look gray.
The screen (G2) control behaves similarly but is a lot more coarse.
If your display is dim, what you actually want to adjust is CONTRAST. That should make things get brighter while keeping what is supposed to be black actually black.
There's a degree of interaction between the controls, so you may have to futz with them both.
If there's still too much red you'll need to adjust cut-off/gain, usually on the neck board. If there's too much red on dark spots, turn down the cut off. If "bright red" is too bright (brighter than the other two primaries), turn down gain. Cut-off is sometimes called bias, and gain is sometimes called drive.
But yes, an important first question was how it looked on the original SFII hardware? If it looked good, go ahead and do the adjustments described. If it looked bad too, you may have a fault that isn't simply adjustment related.