Grey bars & weird beaming

I imported a .musicxml file made with Music Scanner. I can see that it’s probably quicker to just create the whole thing from scratch, but I’m studying how MuseScore works so as to get efficient at editing — and so would love to understand what the heck is going in Page 1 of the attached .mscz file. Three questions:

1) There are multiple grey bars. I can’t select them, nor can I see what they’re representing. I suspect they’re indicaing hidden rests, but I want to delete whatever is there.

2) Measure 50 has weird beaming on Beat 2. I already asked MS to “Reset beams,” but the weird beaming persists. How to fix this?

3) M 50 should have a dot on the first note (G). If I try to add a dot, the following 16th-note (Bb) is deleted. I’ve tried cutting the last 5 notes of the measure, then changing the value of the G, then pasting those 5 notes back in. What happens is that they then go into the next measure and delete some of that. Wha?

In all 3 cases, I don’t understand what MS is doing!

(User context: I used Finale for some 30 years, and Pro Composer (Mark of the Unicorn — way better than Finale while it lasted) before that. I can always figure out what Finale is up to, and I’m trying my darnedest to get there with MS.)