Don't worry, your Focus can handle four down towing and the brake system you have selected. If you are going to do the install yourself there is lots of info already on this site specific to the Focus and battery disconnecting. Just run some searches and start reading. If you hire a good installer for your baseplate he should be able to do all the wiring and battery disconnect switch too.
Carter with Patty from Kirkland, WA
'01 Southwind 32V - F53 V10 with '12 Ford Focus automatic 4 down & US Gear aux brake