Merely commenting on the power distribution - and subject to better specific advice from others - I recommend straight from the battery.
Why - the power is cleaner (not as prone to share path voltage drops & interference), and you provide your own protection (fuses etc) and cables (no strain or interaction with existing circuits).
Whilst many things can be earthed/grounded anywhere, not so for "signal" carrying or interdependent stuff - they should usual have a single ground point. (To avoid ground loops and voltage offsets.)
Make sure you ground cabling is at least that of the power feeds (ie, add additional engine-chassis-battery- cabling if needed).
Where to ground? Aha! In "signal" cases, the most important aspect is probably the "single point".
All grounds should be the same having HEAVY wires between the battery-, body/chassis, & engine/alternator-. Whether they are depends on load & cables/connections.
I power my HU direct from battery+ & -, but I don't have any additional amplifiers etc. (If I did, I might ground all to the chassis instead.)
When powering "through" something - eg, your 5V USB Hub thru the Carnetix - usually you would also ground thru that supply - ie, Hub is grounded via Carnetix.
BUT!!! - since the USB might connect to other things that have local (chassis) grounds.... nah - I think I'll leave that for others. (Else I'd suggest it's a suck&see - if there are problems, maybe a ground-loop isolator, a stronger bond, a supression cap, moving the GND etc.)