Yeah, expect it to be over.
The 505lb hitch weight is the empty hitch weight (as calculated from the design but don't be surprised if it's heavier in reality). It doesn't include propane, batteries or anything else, so you can only expect it to go up from there. I'd be surprised if it's below 650 by the time you load up.
Keep in mind 10% hitch weight is really the bare minimum. If you try to fiddle with it, it's very easy to get too low and then the trailer can become unstable while towing.
Honestly, I would be capping any trailer at around 4000lb GVWR with your car and even then you need to be careful loading stuff in the car. A family of 4 with teenagers plus jam backed with coolers and firewood, you might also exceed the payload.