You are on the right track for being concern about high temps. 230 is on the edge of damage. I tow a 2013 Landmark with a F450. I have a deep sump on the tranny, and an extra large cooler. On a 7 to 9%, my trans only gets to 195 degrees. We drove the Alcan to the Kenai this summer without a problem.
On the steeps grades, monitor you temps and as the temps start to rise, slow down, and if possible raise the rpm by changing gears. On the long pulls, you will see the big trucks crawling up the grades at a higher rpm. Use the gears. Good luck