Can I preset this bar to always illuminate Amber (when tapped into marker lights) and turn on spot light using an in-cab switch?

Thank you for your question. You can set the halos to alwasys illuminate amber, but the leds can't.

Does this light bar measure 13.5 inches with the mounting brackets or 13.5 inches the light bar alone? Do the bluetooth halos only run on a remote or do they run on an app on your phone?

hi, thank you for your inquiry, what i want to tell you is that 13.5 inches refers to the size of the light bar alone . besides, all our RGBW halo light bars can only be controlled by the app on the phone at present.