Hi @wookiee_cookiee, welcome to the forums! 
There is not; however the values are also accessible in the Channel Box as Shape Rotation, that’s where you can finalise the values to remove any decimals.
Great observation; this is true, we haven’t found a way around this, other than to scale down the Marker to reach the inner ones. It’s possible we could incorporate selection in wireframe mode, like one can in Maya with normal meshes, and select the wireframe as opposed to the shape. But it’s not there yet. The Outliner + Channel Box is the other option.
Very much depends on what the character looks like and is supposed to to. Characters typically do not exist in a vacuum and generally have a specific purpose in mind. For example, if a character is sitting at a table with one arm resting on the table and the other holding the chin; you might put the upper back, head and arm in one group, so as to control the stiffness of that pose. With the other arm in another group to control that separately.
Yes, very much delayed, but either the next release or the one following it. 
We left precise control to the Channel Box, we think it already does a good job at this. That said, the next release will allow typing numbers into that box too.
As for a template, indeed, this is what Export Physics is for.
You can assign to the original joints, and later retarget markers to their corresponding control.
That stiffness comes from the FK tool currently active (top-left menus in the Manipulator UI). It’s meant to produce a FK-looking behaviour used for posing, with only enough softness to cope with contacts and self-intersections. It can be tuned, but is a little crude in this version.
See the Wrench button on the lower-left of the screen, atop the timeline. Try mucking about with those sliders to see if anything fits your liking.
For a 0-stiffness, you can also use the Pinch tool instead, the little circle icon on the top-left.
There is not. For the Maya mesh itself, you could use the geometry mirroring of Maya, or connecting from outMesh to inMesh between them, and assign each to the Markers with Maintain History checked in the Replace Mesh dialog. But it’s typically quickest to go through the motions. Haven’t found a solid workflow for symmetry on this one.
Thanks for the questions, these are all great observations and room for us to improve!