After getting back to Firefox I found out that there is a new beta feature named SideView that allows showing two pages in the same tab: https://testpilot.firefox.com/experiments/side-view
Not sure why they restricted the side view width but overall it seems to work quite good.
But, does this address the #1 issue?
A lesson for Firefox (and the rest of us here) Don't remove useful features - these are often the first thing to go, they've been there too long I suppose, in favour of some new fangled thing that often gets low rating responses.....