I know what you are saying.
. I too often have a large Style tree.
1. I think that is not possible.
2. Although RC should have an intelligent way of routing through the style and not consider the paths that are not in use somehow everything is slow when the style is complex.
The only way to speed up is to temporarily disable RC object and I do that via RC lister to prevent Editor to reopen.
3. Unfortunately, converting everything to a macro will not help but if you need to make a macro out of the existing style you can copy everything except Segment, Spline, and Surface objects. I use a trick to accomplish that. In the existing Style right after every Segment insert one Transform node and name it like the belonging Segment. Then delete all Segments, Spline, and Surface nodes and copy/paste everything to the new Macro. You have to make new inputs but now you have all Transform nodes that will help you to navigate where to connect them all.
Best regards and happy New Year!