Whoops, did those first two options’ aspect ratios incorrectly. I calculated against the 720×480 (4:3) resolution, when the TV’s aspect ratio is actually 16:9. Redoing that math.
1. line1x – 576×324
2. line2x – 768×432
3. line1x integer multiple to 4k – 640×360
4. line2x integer multiple to 4k – still impossible
With that aspect ratio, line2x (option 2) is actually going to be the most zoomed in because there’s 1.77x more pixels in the overall frame but 4x more active pixels. So line2x may be your best choice overall.
So in line2x mode, that’s
V. Active 432
H. Active 768