Dasaita 13 Install issues on my 2014 CM Limited with JBL

new to Tundras.com - what an awesome resource!

just purchase my Dasaita 13 for my 2014 Tundra CrewMax with JBL. I have a few questions and one problem that I hope the collective brains here can help with:

1. The new unit comes with 3 USB and 1 SIM reader; did you make them available to passengers or did you bury them behind the radio?
2. I subscribe to XM radio, but the new unit does not natively support. I can access my XM app through CarPlay, but that uses data from my cellplan. Are there any other creative solutions for this, ie, a XM receiver connected to an aux port, perhaps?
3. Can I use the OEM GPS or XM antennas?
4. Netflix, Youtube, etc. viewing. People claim they do it, but I get a "no network" error message when I try the native app. When I play Netflix on my phone I get audio, but no video. What am I missing?
5. Networking. 3 networks are available: Mobile, wifi, and Bluetooth. I understand Bluetooth and its link to my phone. But what's the purpose of mobile and wifi? How do others use them? Is a Mobile SIM required for Netflix?

And I now a my problem. The only sound I get is from the front speakers. I've adjusted the amplifier, adjusted the app, picked the right cambus setting ("8", per support), but still no sound in the rear speakers or sub. I have contacted support, who asked for a pic of the 2 connection plugs. Any insight/suggestions are greatly appreciated.
I have been contacting support via email, but because correspondence is in China I only get 1 email a day from them. I really would like to speak to a person. Does anyone have a contact number that actually gets answered?
Apologies for the lengthy post - TIA for any comments.