Abdiver, the advertised tongue weight does not include the battery or the filled propane tanks.
I have a Sherline tongue scale and have the opportunity to readily check the weight of my toydeck when I load it up.
Your front storage box has its own limit of 150 lbs....be aware of the combined tank/battery/storage box weight as when added together as it might surprise you. Tongue weight adds up. You may want to consider a weight distributor to help offset the tongue weight when you load the box.
2012 FR Flagstaff T12SDTH
1996 Shadowcruiser Pop Up Truck Camper
1967 Newell Motorcoach
2003 Ford F150 5.4 V8 Triton Super Cab
2004 Nissan Titan LE 5.6 V8 4x4 Crew Cab