We never travel with water in the tanks. Most people don't. We've always camped where we either have a water hookup or are able to fill the tank when entering the CG. And you can visit the dump station before you leave the CG. That may not be possible if you are planning a lot of boon docking. Just something to consider.
Always plan 13% tongue weight if you are unsure of actual weights. The trailer weight does not change. The tongue weight calculation is to be subtracted from your available payload. And don't forget to include the WDH weight as well. Could be as much as 100#.
I'm curious, you did not mention, 2wd or 4wd?