For your peace of mind.
1-3/4 = 2000#
2" = 3500#
2 5/16 = 7000 or 10,000 or even 12,500 and perhaps higher depending on shank diameter and metal composition.
3" are higher yet.
Above 16-18K they usually go to a pintle hitch or gooseneck with 3".
I think they even make a small 1" but not sure.
The most important thing is that the hitch on the traier is the same size as the ball.
2" hitch will seem to work on a 1 3/4 ball, but is not safe.
10-15% on the tongue of the trailer is about right.
It's more important not to be to light rather than being slightly to heavy on the tongue.