WD hitch TW rating as close to actual TW as possible?

If you're purchasing this trailer from a dealer.....they should have a tongue weight scale to tell you precisely what that tongue weight will be before you tow it off the lot
Guestimate how much more weight you might load up in the front of that trailer and go from there.

An investment in a tongue weight scale might make sense also.

https://www.propridehitch.com/sherline-trailer-tongue-weight-scale/