I once read of that you have to have at least 30% of the total weight on the front axle.
After weighing you can calculate that percentage, or put it in my motorhome tire pressure calculator.
Or give the details here of tires and weiged loads , then I will do it for you and give a picture of the filled in spreadsheet.
If you then also give GAWR's and GVWR, I can make the picture complete, and it gives also weightdivision, used percentage of gawr etc.
For the suction when a truck passes you can also keep as right as possible , if then the Truck keeps as left as possible the suction is less.
First you have to weigh the motorhome in the way you drive it, so fully loaded.
There are ways , even with a normal truck-weigt scale to measure per wheel( pair). And seperate wheel(pair) weighing would be the best.
This is by driving over the scale with only one side of the vehicle , if there is enaug space besides it.
Then substact that wheelweight from the first measured axleweight to get the other side of the axle.
But with a large overhanging motorhome, the front gets lifted up and with that the alignment chanches , so new alignment should be done fully loaded too.
My opinion is that you should first weigh and get the pressure right.
And it might prove to be enaug, and you dont have to chanche anything else.
But dont use the pressure/loadcapacity lists the tire makers give in America , they lead to to much deflection in the lower loads , wich you will probably need. That is why they stop going lower at a sertain point ( most 75% of maxloadpressure) and for verry low loads it would even give to high pressure, And you still experiënce to light stearing.
The light stearing is mainly courced by the low gripp because of the high pressure for the load.
Also before looking in list add 10% to the weight for reserve.
Then use my made lists wich take care that the deflection stays the same over the whole range , and so allows to go verry low in the pressure.