Sounds like you have it all dialed in, how do you control volume?
I can't remember the name of the app, but when I first installed it I used an app that adjusted volume via gesture control. Realizing that was crap, I noticed there was a remote volume gain connector on the amp. It was a 3.5mm connector and the amp came with a knob with a 3 foot cord, so I just mounted that into one of the blank buttons on my car(99 Cougars have a row of 4 "buttons" above the HVAC controls, but only 2 of them actually do something) for a physical volume control.
Having said that, I use CarHome Ultra as my "Springboard". I used Target Home Launcher to make that happen. Then I use CarTunes for local music playback because of it's gestures. Oh also I drilled out a hole next to the tablet where the mic is, and inserted one of those little black trim pieces that holds LED's in place to make it look good, so I could use Voice Control for searching for music or using Google NAV.
I normally LOVE Apple products, but I found that for an in-car setup, you can't beat an android tablet with a good rom and appropriate apps.