> 1.) Internet connection doesn't disconnect unless you lose service

This works (for me) if you enable powersave mode. Otherwise it stays on.

> EDIT: 8.) The Drive app does not open anymore. Navigation works

I had a similar problem. It turns out it was related to the navigation voice I had chosen. Try to reset the voice to its default in settings, then the app will load, and you can download the new voice you want and after that, switch to it.

I hope you can fix your issues soon enough.