You will want to search and find Uniroyal tire inflation data.
I have Michelin tire charts but that's all. Figure the weight on each tire and then look up the exact model and size of your tire. The chart will tell you what cold pressures should be for your weight. You might want to consider adding the weight of any passengers not in the RV when you weighed it and the weight of water, food, clothing and gasoline depending on how you expect to be configured when you will be on the road with your RV.
Since you have only axle weight, you should assume even weight left to right. For the front that would be 2040 pounds each wheel. You will need to divide the rear weight by 2 or by 4 depending on whether you have a single or dual tires in the rear.
For your add on weights, decide if the weight is over the front, rear, or center of your axles and figure accordingly.
Having your RV overloaded can be a serious issue so it's a good idea to go through this analysis as you are doing.
Gary, Cindy, Reacher (Maine Coon), and Vivian (in spirit only now).
Retired: July 31st, 2013 and loving it.
2011 Coachmen Encounter 37 TZ pulling a 2012 Wrangler Unlimited Sahara. Many upgrades, additions, mods, and changes.