As a minimum you should file a complaint with NHTSA
. I don't think the RV dealer is being a responsible seller as most reputable dealers have the tire warranty clock start ticking on date of sale. Sure hope you got a great deal on the "AS-is" RV.
Until we hold the tire company responsible for the stuff they sell we, the RV owners will never see an improvement in quality.
What is the claimed GAWR & GVWR on the plate on driver side, outside driver front side of the RV?
You need to find out the max inflation rating of the wheels, in writing as you may need to change wheels too.
If they refuse to give you an inflation max then you need to find wheels in your size that came on RV delivered with LR-E tires.
I hear that eTrailer can help with wheels.