It should get quieter over the next couple weeks. Mine was pretty obnoxious when I first fired it up. Luckily, I'd seen a couple in operation other places and knew it could be quieter! And it eventually settled down.
Regarding the skimmer box, sounds like you have it set up right. Kinda weird the way they designed that, isn't it. You hang the box off the pump, which in turn hangs off the tube, which hangs off the skimmer. Make DARN sure those clamps are all tight that keep everything hooked up to the skimmer! (Not a big fan of that box... guess that's why you can find mine "For Sale" in the classifieds! Never even been in saltwater!)