The error was:
bits[1] is undefined
var vars = bits[1].split('&');
on ImagePlus.js (line 78)
i changed it to
var vars = bits[0].split('&');
and the TV input shows up, but I really couldn't explore further. I am pretty sure that's not an actual fix.
As for the scaling, I'm not sure I get you. Do you mean to say that, given a source image of 500x500px the minimum marquee size would be 500x500px? Or are you talking about the max marquee size?
To clarify what I meant, if the target image is to be 100x100px, then given a source image of 500x500px, the marquee could be anywhere from 500x500px to 100x100px, but no smaller.
I am sure that I can make more pointed comments when I see it working in its current state. Until then, it's all a bit abstract. :O