Sometimes locks like that you can drill the tumbler out and get it off. Get a cn of Fluid Film and spray it inside all your locks. That stuff works great !
That's not a bad deal at all, they give you a mounting plate with your winch, I bought a 12,000 lb superwinch from Summit and they didn't give me a mounting plate, matter of fact they didn't even give me a hat and stickers either, I had to go to Harbor Freight and buy a mounting plate for $40.
First use you should run the line all the way out and put some weight on it and wind it back in. That way the line wraps tight on the drum. Otherwise the line can spin on the drum from being too loose and cause the line to bind up
I like that winch mounting system. I myself will have a bigger winch for my trailer. I have a 4500 on my 300 4X4 ATV. I'm thinking somewhere between a 9000 lb - 12, 000 lb. I will be mounting g mine inside the box, keep it out of the weather, and be able to pull a vehicle closer to the front of the trailer. Definitely going with the wireless system. I love the rope on my ATV but think steel cable might be the best for the trailer. Another thing to always keep in mind is choosing the winch with the best line speed.
Rolling weight and static weight are two different things. Your winch is designed to pull 5500 pounds of static weight, that truck might weigh 4000 pounds but it is rolling weight so the static weight is about a third of that.