we purchased a mini lite ETC 181 which has the murphy bed. We dont have the couch but instead have dinette under murphy with aluminum frame so similar weight overall. Our tongue weight is 457 on CAT scales when fully loaded. Dry tongue weight of 365. You should expect similar increase. Our tank sizes are the same and typically on the road with 1/3 tank of fresh water but gray/black empty.
We love the layout of the 25ks/2503S but it is too much trailer for our old 2002 Tundra 4.7l. Enjoy your new toy
Roy & Jean
2010 Rockwood mini Lite ETC 181
2002 Toyota Tundra 4.7l 4x4
Prodigy P3, E2 WDH