Proper tire pressure?

I thought this sounded dangerous to me, especially traveling at 75 to 80 mph pulling a trailer. I have been on trips where I use the interstates, but I hold my speed to no more than 65 even in the areas where the speed limit is 70. It makes sense to be because it feels a lot safer, and I think it saves the trailer tires too.

Thanks for the responses to my post!