Hi Moisheh,
I do have a queen bed, sofa and dinette. I also have nearly a full size shower on the passenger's side with the water closet on the driver's side.
I have weighed mine, including doing each set of wheels by themselves.
I have no slides and I'm nearly above capacity, and the driver's rear dual was not over axle capacity but was over tire capacity. So near that I changed the rims and tires to get myself into a comfort zone.
Be careful about length to wheel base. For the 176" wheel base 26 feet is 55% (ideal), 28'5" is 51% (ok), and 31 feet is 47% (not good). Anything below 50% is MUCH harder to drive.
E-450 tops out at about 14000 pounds. Class A chassis with a V-10 is, if my memory serves, 22000 pounds.
For what you seem to want I think a small class A may be more appropriate.