I didn't see the horizon as 'off'. The hills rise and fall, so you can tilt it either way (a bit) without a problem. I agree with your suggestion re the lower right and upper left dunes. Composing for them together should work.
Another thought, this time on #2. When I crop the bottom to make the leading line go to bottom left corner, it looks better to me.
BTW "foreground" is spelled correctly.