Regarding selection (Bug #2, above) …LightBurn uses a CAD technique that I find very helpful: Drawing a rectangle down from the top left means, “Select all objects that are completely contained within the rectangle and ignore those that aren’t”…whereas, drawing the rectangle from the bottom right upwards, means “Select any object that intersects with the rectangle, even if it’s not completely contained”. This is a really convenient feature that would be a big bene in your selection woes (bug #1, 2, and 3).
The 75% SVG is a known issue revolving around the assumed DPI being used (72 vs. 96) and the use of pixels to specify size. There’s a thread on this Here. In LightBurn, the developer there just implemented a “tolerance” for CC created SVGs to compensate for it.
On the suggestions:
I second all of the CC Recommendations.
For the CM Recommendations, the ones that resonate for me and I second a desire for are: 1, 4 (and my suggestions Here), and 6.