I have a B&W turnoverball hitch in my truck as well, but I (as have most of us with this hitch) chose to use the B&W Companion 5th wheel hitch. Rather than hijack the thread, I'd suggest using the Find function above to run a search on "gooseneck adapter" to get lots of good discussion on this subject.
Insofar as safety chains are concerned, these chains are subject to inertial shock loading, not just a steady pull. I'd suggest working with a qualified trailer shop or trailer hitch shop to determine your needs and get the appropriately rated chains.
On Edit - take a look at the gooseneck trailer safety chains (3rd item from the top) HERE
. By the way, the empty weight of your trailer doesn't mean much unless you intend to pull it empty. I would suggest going by the trailers GVWR plus a safety factor of as much as 50% to 100% (but then again, I'm an engineer - I'm paid to be conservative