The features you listed as needed are not "live" functions, so you don't need to keep the Tazer connected for those to continue to function. I use mine for the same things (tire size, gears + LED headlight/taillights, AUX switches), I don't keep it plugged in and I haven't had any issues with...
I just installed my 2nd pair of Heavy Duty Scrubblades after 1 year of use. I'm happy with them. Over that time, the top-facing surface of the metal arms faded and started rusting, but the blades held up well.
Definitely recommend a DC to DC + MPPT charge controller. If you're out for multiple days w/o regular full sun on your solar panel(s), it's nice to be able to rely on your alternator to charge your aux battery while driving. I'm a Redarc fan but they are expensive. Attaching my wiring diagram...