Dry is fine.
All the classes I know that have a min weight are measured dry. Score chassis tags require the car to be wet and in race trim. Calculating fuel is easy, just by looking as your pictures I would guess your fuel cell is 20-22 gal? At 6.15 lbs per Gal that is another 123-135 lbs.
I'm with Matt I think most of these cars need to go on a diet. Hitting the 1800 lb mark would be great. I think in order for the UTV to be competing with the 1600 cars in time, they are going to need to be in that weight range, and I still think the rules need to be adj to allow a bigger tire, up to 33 inch maybe? That is the standard size tire in all the limited buggy classes. I think you guys would be shocked to see how much bigger of a hole you can go over vs. go into with a bigger tire. Then again I'm still surprised to see teams choosing to run tires smaller then the 30 inch allowed. A course then you will a new challenge in the CVT dept as I dont know if the belts could handle a 33 in tire for long.