Glad everything is up and running. Here's a few tip to keep everything running well.
1. Wire nuts are not made for automotive wire (wire nuts are made for home wiring which has solid conductor or stranded wire with fewer thicker strands, the wire we use has much finer wire and many more strands) and will not be reliable in the long run (they were not designed to be in a moving vibrating vehicle, they are made to live in a snug little box inside your wall). Go get some
crimp caps and a crimper, they will hold up to vibration and general abuse much better.
2. Zip tie those wires up! It looks better and is far less likely to get them caught on something going into or coming out of the trunk.
3. Screw the box to the floor, velcro is almost never enough, and the adhesive on it will give out. Or csrew it to the opening behind the back seat.