I’m not sure why you need to make those adjustments. From the numbers, it seems you’re using the CPS2 values (although H samplerate is incorrect, 3×512=1536), which is not correct in the first place, also for x4 mode you should not multiply by 3, but by 4, so it doesn’t make sense to me. With those values, you’re giving the display some real funky timings.
The default 390 multiple (4×390=1560) should be correct because it adjusts for pixel aspect ratio of the source, no matter if the playstation is in 256×240 or 320×240 modes (depends on the game).
In general, I do think this should be more easily solved by the TV’s image zoom functions (although not all TVs have those of course). I also remember BonzoBit saying he had to reduce back the V.Active to 240 to get correct aspect on this Panasonic (it’s somewhere in that thread). No idea why, but I guess the panasonic can not interpret the 1280×1024 5:4 aspect ration in the manner we want. If it could display it at 1:1, the aspect should be correct.
Can you post a picture of how the screen looks before/after adjusting any horizontal values?