You can still establish a connection with a tablet by using the PDANet/Foxfi Bluetooth DUN function--you just have to install PDANet for Tablet on the tablet. The connection speed isn't as fast as the wifi tether, unfortunately.
I am curious what the Speedtest.net test on this build of Android 4.1.2 would show over a Bluetooth tether. Can someone run it and post it? I don't have a tablet or the app.
I tried that--the Speedtest app can't measure it, because it isn't a true data connection. I haven't tried using the web-based Speedtest.net, but it can be difficult to access on mobile, because it usually deflects you automatically to the Speedtest app page on Google Play.
No. Unfortunately, iOS development is about bureaucracy, not technical ability.
And Open Garden, which uses Bluetooth for p2p internet sharing, has the same problems with a lot of apps not recognizing connectivity. This is a problem with the Android OS's ConnectivityManager not detecting VPN as a mode for connection.... a representative on the bug tracker said that it would be fixed in at 6 months or so (about 2 months ago): https://code.google.com/p/android/issues/detail?id=33666#c31
But who knows when it'll really be fixed. In the meantime, tell all your favorite apps to STOP using ConnectivityManager or at least to check for connection through VPN as well.