Tim, I would not attach anything to the car's 12 volt system for any reason. That battery is very small and does not have a lot of capacity. Your brake system could easily discharge that battery depending on how ofter the brake system engages. Since you bought a proportional system my assumption is that the system will engage at also every stop. You will kill the battery if that is the case.
Yes, u r right about not connecting directly to the FFH battery. I've gotten mixed up between two topics that r related to what I'm doing I think I'm good to go on seeking the 12v full time power source. Either the jump start unit or going through the firewall. Now, I'm making the breakaway switch my main priority. I've gone too many years without one and now is the time to do it right. However, I wish the breakaway kit didn't have the plug connected to the wire. It requires a much bigger hole in the firewall. I think I'm going to cut it off and reconnect it after I snake it through a hole.
BTW: isn't the Patriot a proportional system too??
Finally, when I get the email notices about replies, I can't reply there. They r returned. After awhile I find them here and I can reply.