I'm not an expert, and recently got my own Firehawk, I'll try to respond from experience.
1) I don't know, haven't gone that far in.
2) You can do this in basically 2 ways, 1 is to use one of the FX slots as another drive or boost or whatever. Since there's the normal stompbox slot and 2 FX slots, you can use any of the FX slots to put 2 more drives, or delays or filters or any of those. In this way, you can have up to 3 drives stacked, you can move the FX slots in the signal chain from within the app, and place them anywhere, but not before the WAH. The other way, which I recently saw in another post, is that you can use the FX Loop by connecting both cables from FX Loop send to return. This way you can assign the FX Loop to one of the available pedals, and change the settings on the FX Loop depending on how many dbs you want. Just turning it on from default gives a loud enough boost.
3) On the Android version I haven't seen any New Tone option, you have to start from one of the presets in the board itself, and you can save it to My Tones without having to overwrite any of the existing presets in the board. The last 3 banks (30 31 32) are empty, so you can use those if you want.
As for the Bluetooth, the FH should pair only once and work with no problems as long as you don't turn off the unit or the android device, it will try to reconnect and sync as long as the BT connection is still on if the android device was turned off for a moment. This is actually on the manual.