I think im wrong. Second battery wiring. *pic attached*

The first image is how im currently wired. Is this ok? I have a couple questions.

1) should I do the second image, and run amp from my xs5100.

2) should both battery be grounded to chassis?

3) since im in a chrysler 300 and my battery is in the trunk. there is a positive charge post up front under the hood. will this charge the system properly with my agm charger.