Welcome to the site .
lots of info on here.
They rule of thumb is to dry the sticks naturally is 1 inch thickness per year.
I know nothing about the type of wood you have but if you dry it to fast it will be more of a chance it will crack you could seal the ends with something paint or wax will help but i never do.
As for the diameter of the shank I think 3 inches is far to big for a stick .I work mainly with a 1 inch diameter or just over , if the stick is sound it is more than capable of giving support.
I mainly work with hazel shanks there light strong next have a degree of flexibilty.and mainly make hiking poles. which is something you would want for that type of walking.
Hill walkers generally go for either thumb sticks or the hiking pole..
A thumb stick should be about the hieght of the elbow jiont give or take this is personal taste. A hiking pole should come to about the hieght of your armpit.
The american market however is different to the standards i would work to, you tend to go for the larger diameter and slight taller , its just a matter of taste.
Personnally i wouldnt use a shank above 1.5 inches in diameter.and definatly wouldnt use it if i couldnt straighten it .A shank thats not straight tends to be weaker.but no doubt some will disagree with this.and if it has a knot on a slight bend you wouldnt be able to straighten it. i would ditch it. this is one area the amercans wouldnt agree with.
I do work to the british stickmaker guild standards it would be interesting to see what the american guild standards are.
But mainly and this is important its a fun thing and thats all even though i do sell my sticks.