Okay I tried the test theme and it seems good vertically so far re right side footer widgets touching left widgets, That issue does not appear to be happening now.
I’m still getting a large white space under the widgets on 125% zoom and 769px and 110% and 768px controlled with the margin-bottom: -50px; in this example. 100% seems fine.
The CSS in your/my post above doesn’t appear to correct this issue either so I guess that means the grid moved horizontally at those to points.
Cheers