That version does not support containers extension. It has only basic built in support.
Firefox ESR has thousands of open bugs, and possible exploitable flaws. And I don't presume the current tip will be much better. I don't think the fixes you presented make much difference. Also a hacker more probably will attack tip and ESR.
I'll faster go to Palemoon than returning to Firefox in the near future.
meanwhile, all the security patches you're missing out on: https://www.mozilla.org/en-US/security/known-vulnerabilities...
at least use ESR 52, which is only 1 release cycle out of date as of today.