1) about half way up the trunk, there has formed, (what my wife calls a “knuckle” I’d call it a knot...
Any ideas what, or why?
I think I see what you mean.
At this point, it is kind of late to do anything about it. If you cut it back, it will severely set your cherry tree back, which is something you don't want in your climate, because cherry trees can be kind of difficult to grow and slow growing there.
It probably originated when the leading tip got damaged, when the tree was much younger, so it could not keep growing straight, and there was an offshoot branch very close to the tip that started growing. It will probably be okay, but may not be the most ideal situation, since it will ultimately make the top leading branch weaker and easier to break when it grows bigger and becomes heavier.
On the other hand, at some distant point in the future, assuming it does not break, then eventually the knuckle will start being grown over by the expanding diameter of the trunk and be less prominent.
One thing you might try doing is girdling at the knuckle point to prevent all the growth from continuing to be directed there. Then hopefully the tree might send out another leading branch below that line.
If you simply just lop off the top, growth is still going to be directed towards that branch above the knuckle point, and it will likely send of another two branches.
Girdling right below the knuckle point might be a better way to go. Since this is a less desirable branch, you could also of course then cut it back to whatever desired height you wanted to maintain.
But consider this: If you cut it back and then allow it to keep growing after that, you may likely have another knuckle!