>Could the problem be related with the font size (Arial, 13) and using 125% for size of text, apps, and other items in my Windows preferences?

Yes, that is exactly what causes this problem.

This resizing option at browser level should never have been invented. This devastates pretty much the entire content. All the images are very poor quality. Indentation and spacing are being broken. I would also find it extremely hard on the eyes to have something in such low precision.

IAC, there is a bug in Chrome when in over 100%. The dimensions returned by the browser are not right. This is why you end with a scrollbar. This is extended support that is very difficult to maintain. I would assume their next version would or might fix that.

BTW, Chrome does a poor job on Calibri. So, on that one, Arial will be used all the way. You should have better toolbar text now as well as headers at a few locations.