I second everything above. I want to second the above so you know there's more than one voice for all these issues. I'll give more detail in a day or so.

But let me add this:
You've changed the Image Size---but you've added 3 clicks to GET to Full Size.
Three.
Please understand, lest you think this is trivial: Many artists don't even like to do "one" click: Do you think 3 will make it easier?

If you want the Full Size to work, please---please---eliminate the middle-man. Go from Display size to Full size in one click.
Know that we can figure-out the "scrolling" thing: Zooming's not supposed to be a 'breeze': It asks that we spend a few minutes on art. To study it. Contemplate it. The Display size was always 72 DPI, the FULL size was whatever resolution we chose. The Full Size is sharper, deeper, w/ better hues. PLEASE remove the extra clicks! Just remove them. It's simple---just remove them. Thank you. Mark