As long as you did not weigh, you best go from the Gross axle weight ratings ( GAWR. Rear add for smaller motorhomes even 18% because for those real axle load begins at GAWR and often a little overloaded .
Then I mean GVWR ( gross Vehicle weight rating ) of below 3500kg/7700lbs.
Front thoug seldomly comes to its GAWR or you must atach a motor on the front bumper.
So front can do with much lower pressure.
This does not go for dual load rear axles ( 4 tires on the ( imaginary) axle).
There front mostly bit higher pressure then rear.
But if you can produde the right data , I am able to calculate it for you with use of my made spreadsheet , in wich I even use a better and saver formula then the official used formula.
Will give copy of text I used for other topics ,so I dont have to write it all over again , but can be little off topic her , for general use.
Tirepressure advice is all about load on tire and speed ( and sometimes about alighnment - camber angle).
So if you can give details of car and tires , I can calculate an advice pressure with some reserve for things like, pressure-loss in time, unequall loading R/L, incidental extra load, misreadings of pressure scales,and misyudging of weight, etc.
This is from tires next and can be read from sidewall:
Maximum load or loadindex.
Kind of tire to determine the AT-pressure/pressure needed for the maximum load up to maximum speed of tire, or if lower 160km/99m/h/reference-pressure, wich is not the maximum pressure of tire.
Maximum speed of tire, most given as letter ( Q=160km/99m/h,N=140km/86m/h fi)
If you have offroad or tires looking like that , with large profile blocs that cover a part of sidewall, also mention, they are allowed lesser deflection then a normal road tire, then the tire maker used to determine the maximum load (to my conclusion the case for the Bridgestone tires on Ford Explorer in the Ford/Firestone affaire).
If you cant find all of it give sises of tire and Loadkind, then I will google for it.
From car next and mostly can be found on same plate as the original pressure advices:
GAWR and GVWR ( Gross Axle/Vehicle Weight Rating)
But best would be to determine the real weights in your use on seperate tires or estimate it as acurate as possible, by weighing per wheel(pair) or axle.
Maximum speed , you dont go over for even a minute in your use, eventually different for different situations, for instance when towing or fully loaded.This apart from trafic regulations, if you drive faster then allowed give that speed. Nature punnisches with tire-failure, police only with a penalty.
Give all that and I will calculate and give a picture of one of my filled in spreadsheets in my answer.
Greatings from a Dutch pigheaded self-declared tire-pressure-specialist.