You know what Session also has? Well it ain't forward secrecy.
Devjavu
Are the only countries with a death penalty so far
Please also consider things like canvas spoofing. It will create a unique fingerprint that is different every time.
Oh no the radom dude online who speaks another language made a quick mistake. Better make sure to correct him! Why do people always get a boner from grammatics? Its ridiculous! (hehe)
Is that it's name? Awesome
Would you mind telling me why you switched?
Not everyone, but lots.
I want the drugs you are on
Money
Yes to all of those. LIFE ON THE EDGE BABYYY
You can only know if you choose to read the code and compile from source. You can trust, in that your read the code and just install the app, or let others read the code for you. If reputable sources tell you it's good, most of the time it's good. How can you trust Signal more? Well you... shouldn't. You could try to use a decompilation tool, don't know if that works on Android's apps though.
Session does NOT use the tor network. They use their own, smaller, way easier to take over network.