Best Marshmallow upgrade route

Hi,

So I keep reading all the 6.0 threads and have yet to come up with an answer. I am thinking of moving to Marshmallow. I have a few things I would like to keep and would like help understanding if it is possible at this point.

Upgrade to 6.0
Get adblocking of some type(either though app or modify hosts in recovery)
Verizon tethering check
Android Pay

I know I can use an app for tether, so that is 1 of 3 taken care of. Can someone help me answer the other 2? Will I get boot errors saying my device has been tampered? There has been a whirlwind of activity, maybe I'm just getting a little anxious and the answers will come in time.

Thanks

Route phone calls through USB headset?

I've been successful at routing both speaker and microphone audio through a USB headset on my OPO. In fact with Skype and 2 other VOIP applications it's just plug and play. It works with no special effort. But with regular phone calls, the phone completely ignores the USB headset.

Has anyone found a way to route phone calls through a USB headset?

Running 12.1, Temasek's unofficial ROM.