[kodablah]

Wrt #1, I think the issue is that scrollbar size makes it easier to tell one Tor user apart from another in the Tor browser, not that you can determine they are running in the Tor browser (or even know their platform from a common fixed set). For most users of Tor and the Tor browser, simply checking that they are coming from a publicly known list of exit node IPs is enough (or if they are already hitting an onion service, then it's obvious).