The conclusions you took are all right.
Mayby wrong about the single/duallload thing.
But you forget to build in a reserve.
Needed for next:
Unequal weight R/L on the axle .
Inacurate reading of pressure and weight.
Pressure loss in time.
Going over 75 mph for your tires
When I make a cold pressure axleload list I make them for a bit virtuall higher speed, for your tires for instance 87 mph ( not saying you must drive that) and give 90% of calculated axleloadcapacity for the cold pressure.
This then still. Gives acceptable comfort and gripp, so I concluded from reactions.
Then you dont need to do pre or after calculations yourselves.
Then you " only" have to determine the axleloads (better would have been axle-end loads) 99% accurate, wich you did by weighing.
But did you weigh fully loaded?
This determining axle(end) loads accurate in your use, is your responcibility.
I assume the trailerweight on the weightslip is the tag axle, but correct me if wrong. Then same tires.
And you have the top tires in the list so maxload S 3970 lbs / D 3750 lbs. At 110 psi , but also correct me if wrong.
I estimate pressures determined with use of my made list will come to about 100 psi, and still acceptable comfort and gripp.
Then about what cold pressure is.
Best definition is when temperature of gascompound in tire is practically the same as the outside ambiënt temperature.
That is when not driven long enaugh and no external factors, like sunshine on tire.
This last has become the definition .
Now there are 2 camps in if recomended cold pressure is for a certain ambiënt temperature.
Camp 1 is largest, and states that you have to fill the determined needed cold pressure at any ambiënt temperature , be it 20 degr F or 110 degr F . Gives you a chalance to fill up and blead down when traveling trough extreme ambiënt temperature regions.
I am in the second smaller camp, that states that determined needed cold pressure or recomended is for an index temperature given
Read index temperatures ( As RIMEX cals it) between 60 degr F/ 15bdegr C upto 77 degr F / 25 degr C .
Mostly 20 degr C / 68 degr F.
Porche and BMW give on tmps screen besides the pressure also the recomended pressure calculated from index temp ( most likely 68 degr F) to the temperature in tire ( also sent by the sensors) . Some tmps systems for motorcicles give on screen pressure calculated back to 20 degr C / 68 degr F.
A tmps system is yust a little computer in wich the designing ingenieur can put software he thinks needed.
This then can give differences between tmps reading and gauge-reading.
My opinion based on conclusions I took in time is that you can let the pressure flow with temperature change.
When hot the higher pressure gives lesser deflection, so heatproduction at same speed, wich compensates the lesser cooling down by lesser temperature differences between tire-material and in-and out-side tire air ( or other gascompound) .
So never blead down cold or warm pressure on a hot day.
When cold ambiënt the other way around.
More heatproduction and more cooling down.
But then you may highen up to determined needed for reasons of riding quality and fuell saving, but not needed for savety of tire, so no overheating tire-material, wich is main goal of tiremakers when determining needed pressure.
If the camp 2ers are right, you only have to check if pressure and temperature are in line, and dont need to fill up and blead down maniacally.
Tmps systems give a direct warning when pressure drops 2 psi .