>>15First of all, The TOR browser doesn't allow to browse the "open web" freely. It allows you to browse within the Onion network freely and unmonitored but when you leave the onion network all of your traffic can be seen from Tor exit nodes unless you use a VPN or proxy from the start. But if you had a VPN why would you need the Tor network in the first place? I guess it is another layer of security but it is rather unnecessary unless you're actually doing something illegal.
Second of all, Since Firefox is completely open source so you can view the source code so if it was truly tracking you it would be able to see it there, and if you still paranoid you can even use a older version of Firefox and build it from source.
Happy browsing.