If you want to post your numbers, we can try to help you make sense of them.
plus how close to those maximums I can safely go?
IMO, you can use it up to the maximums. Given the number of people who tow over them with no immediate ill effects, I think it can only be assumed that these numbers are safely padded. (Though, for me- I'll do what I can to not exceed them.)
Also, how to most accurately measure the king pin weight in my truck?
The way that I calculate it is via 2 weighings of the truck:
1) with the truck + camper getting weights for the front/steer axle, rear/drive axle and the trailer axle(s)
2) with just the truck getting weights for the front/steer axle and rear/drive axle
Essentially the difference of the sum of the truck axles loaded (#1) minus the truck axles unloaded (#2). The only caveat is in situations where you're unloading weight from the front axle - in that case, I think you should subtract the 2 rear axle numbers to get your pin weight.
Finally, here's a 4-part blog series on my weightings for my truck & camper:
Learn To RV: Getting Weighed - an adventure at the CAT Scales