Feel free to ask anything. If I can't answer someone else may be able to.
1. Explode. No. I didn't explode, I just edited the node.
2. Edit mode. Yes. it may be just my terminology, but I class edit mode as seeing all the individual nodes one at each vertex of the shape + others at the mid point of arcs.
3. Position. Depends. Yes, you do have to be a little careful some times when moving nodes especially on arcs, In the the #Edit # I did to my post above, in your drawing just snapping will produce a slight 0.0027" difference, compared with he opposite side.
Sometimes it would be necessary to set some thing up to ensure snapping to an accurate point (s), for example, snap a cross to the opposite node vertex. mirror copy the cross using the centre of the large arc (C seke), as the first mirror point, and holding down shift key to create a horizontal mirror line. Then adjusting the node (s) to vertex snap to the new cross. (see mirror1 attached).
There are other ways, for example, in some cases, one can select each end node, and use intersect (I) seke to snap both ends accurately. The actual method used will differ depending on the situation, if the two ends were very close but didn't actually overlap, then intersect snap won't work.
4. Trim. Not in this case. Trimming uses a second line / arc etc. as the 'trim line'. In your case, because the inner shape is essentially one polyline, there is not a second line to trim to. In some cases, yes, you could set up a line to be used as a trim line. for example, in your drawing one could snap a vertical line to the opposite end of the large arc, and trim both overlapping ends to this line. However when trying that on your drawing it left a tiny gap where the two arcs don't quite meet.
As for escape. for just checking nodes, sometimes I will select a node to grab hold of it, and move it to see if it is one node, or two on top of each other. When I move a node just for testing, like in this case, pressing escape will release the node back to where it was, without physically moving it. An alternative would be to move the node then use Undo, to put the node back to where it was, but that's more work.
### Edit ### Just seen your new drawing, will look at that now. ### End Edit ###