theres no way in hell im reading all that, but a motorcycle battery will solve latency issues nicely if you plan on using the system only with the car on.
another battery will stop the lights from dimming
it will worsen the load on the alternator
and it will make your bass sound better if you have a crappy amp with a weak power supply.
I do think you will need to fashion a venting system however unless you use a venting battery.