That is a nice demonstration of your predicament, good job making it!
I have no experience with SU Animate so I cannot comment on specifics with that software. However regarding the speed difference between what is seen “live” in SketchUp vs. an exported video, I’ll mention that I think the scene-switching action in SketchUp has a minimum (definitely non-zero) time overhead. Maybe 1/10th or 1/20th of a second? That time overhead is between each scene, which translates to between each frame during a live View>Animation>Play function in SketchUp. Therefore, I suggest not judging the rate of motion based on what you see in SketchUp when using the View>Animation>Play function where each frame is a separate scene.
So how else can you determine a proper speed, other than trial and error via repeated exports? That depends on the features of SU Animate, for setting the net elapsed time between keyframe positions. That elapsed time between keyframes should hopefully (to my way of thinking) not be determined by the frame-rate value you might specify. I would hope that you can specify an overall frame rate for the entire animation, and can specify the time deltas between the various keyframe steps. With those two input specifications from you, the software should work out how many frames that a given movement would consume (rather than force you to figure out how many frames you want the movement to span). But I don’t know how SU Animate works, which might not fit my view.