Filled in in my made motorhome-calculator, it comes to F 41 psi , R 75 psi.
Googled your sise tire to be loadindex 123 for single load is maxload 3420 lbs, E- load AT 80 psi.
Front that low??!! Yes , search the GAWR's, and you probably discover that rear is already overloaded, and front still have a comfortable reserve.
The vehicle-maker calculates for GAWR's ,and for that it probably needs 60 psi.
Are these the original sises and loadrange ( E- load / LRE AT 80 PSI) . If the weights are right, and tirespecifications I found too, especially the low front gives better comfort and gripp, but you yust gotten used to the kidney-belt:B
My calculator adds 10 % to the given loads( so yoy weighed ? !), and then calculates the pressure with a formula that gives higher pressure then the official European, wich America uses too but only for P-tires since 2006.
So my calculation is certainly not to low.
Determining the real weights is the most tricky part, in this all, but you weighed fully loaded, so also all the persons? , wich gives you already bonuspoints.