Tire upgrade air preasure ?

A truck scale isn't going to tell you what the weight is on each tire. Depending on the position you can easily have 500-800 lbs. difference between tires. Depends on where the slides are, and what is in the slides. I have 4 tires that have 2000 lbs. on each and 2 others that have 2500 lbs. on each. The 2 with heavier weights are not on the same side, or in the same position front to back.

Just because 80 psi is the maximum pressure on the tires that you are considering, you should only inflate to the pressure recommended by the trailer manufacturer or better yet based on the actual weights carried by your trailer. Go to a truck scales and do some weighing to figure out the tire pressure you should generally shoot for.

If you went to "E" rated tires for increased carrying capacity, it seems silly to not use all that carrying capacity by running them at 80 psi.

"I decided to split the difference at around 72-73 lbs but.."

Spilt the difference based on? Sorry, Baber, I don't believe you know more than the tire manufacturer. In fact bunches less like me.

What are your rims rated for?

What does your trailer weigh? (these are for trailer right?)

You need to look up the load inflation table for your tires, weigh your truck, and inflate accordingly. Using too much pressure will result in a harsher ride and wear out the middle of the tire. Using too little pressure will create extra heat in the tire and wear out the edges.
Just going by a sticker or the sidewall works okay on cars that always weigh about the same or trucks that stay fully loaded all the time. If you some times drive empty, sometimes loaded, sometimes towing heavy, etc pressure would be adjusted ideally.