@ Benk
When the load on the tire is low , the deflection of the tire is the same , that is what the calculation of pressure for lower loads is meanth for.
So for lower loads you dont need the pressure needed for the maximum load. If you use that the deflection is less so the bending of the sidewall is less.
What I need to make a better estimation of the load on the axles is the empty weigt of the "truck" and the loads that are on it for not towing and towing condition. Then a pressure can be calculated , that is save for those situations. Also try to find the GAWR's and GVWR, mostly on the same plate as the pressure advices.
Also need the maximum load and pressure needed for that ( called maxloadpressure or reference-pressure and is lower then the maximum pressure) , wich is probably 80 psi for your tires( because of the 70 advice back for towing, wich is higher then the loadrange D below that with 65 psi) , and is written on the sidewall mostly or can be made up by the Loadrange ( E-load/10 ply = almost always 80 psi).
Many car-makers automatically describe that 80 psi , thoug the tires are probably oversised for the loads. Could be that even for your GAWR back ( gross axle weigt rating) with a comfortable reserve , you only need for instance 60 psi. But to be shure we have to calculate.