Based on our 29' KZ Spree, I can tell you that the actual tongue weight will be around 950 lbs. Allow another 100 lbs for the WDH and you are at 1050 lbs for payload requirement. Fully loaded for camping for two, we are around 200 lbs under the GVWR and that's with one battery. If we towed with just one full holding tank, we'd be over the GVWR.
For that Spree you'd be looking at about 1050 lbs for payload and about 7K lbs for TT GVW. You'll need 1000 lb spring bars on the WDH. We run 1200 lbs on our Reese DC WDH. FWIW, specs I looked at say over 31' for the 280RLS.
Unless you are going to only go on short local camping trips on flat ground, I wouldn't want to tow that Spree with a 1/2 ton and esp. not with 3.42 gears. We tow ours with a 3/4 ton and have 4.10 rear end. We are just on a trip through the Cascades in Or and Ca and out to the coast and have been on 9% grades and some very twisty roads with frequent speed limit changes. When you say "trips out west" if the roads are similar, no way would I do that with a 1/2 ton or 3.42 rear end.
The first thing I would do is go load up your truck with everything you'd take on a trip (DW, kids, pets, tools, bikes, etc.), go through a scale somewhere and subtract that from the GVWR on your door jamb sticker. Then that's the available payload you've got to work with for trailer shopping. You *could* be in for a surprise. 4x4 will take a fair slice out of payload ratings too. I don't think you'll make it with 950 lbs of TW on that Spree.
BTW, if you plan to put a lot of miles on the TT and on bumpy roads, I highly recommend shocks on that Spree, otherwise you will find there's a lot of bounce at the rear end.