Water weighs 8.33 lbs/gallon. a 30 gal tank will add 250 lbs to the trailer. If your tank is in front of the tires, most of that weight gets transferred to the tongue.
Not necessarily. Depends on how far it is in front of the axle relative to the end of the tongue. If exactly in the middle, it will put 125 lbs on the tongue and 125 lbs on the axle. The closer to the axle from there, the more on the axle and less on the tongue. Conversely, the closer to the tongue from there, the more weight on the tongue and less on the axle.
1988 Coleman Sequoia - popup (1987-2007)
2012 Roo19 - hybid (2012-2015)
2016 Mini Lite 2503S - tt (2015 - ???)
2011 Traverse LT, 3.6L, FWD
2009 Silverado Ext Cab, 5.3L, 4x4, 3.73
2016 Silverado 2500HD Dbl Cab, 6.0L 4x4, 4.10