Towing with FULL, EMPTY, or PARTIALLY Full Fresh Water tank - What do you do?

My 2011 250RS has 30 gallon fresh water tank. Going on our first trip in a few weeks (300 mi one way). Debating on wether to travel with FULL or partial tank. Not sure of water quality where we are going (FULL hook ups), so that is reason for carrying water.

Questions:

1. Is tank secured well enough in the 2011 250RS to travel with a full tank?

2. How much tongue weight will be reduced with a full tank?

3. Can the sloshing of water in a partially full tanks can cause sway?

4. Do you carry, full, empty or partially full tanks? Why?

Thanks!