Broke my stock top cap – What can I replace it with?

I decided to try something new today, namely servicing the headset bearings on my Grizl 7 AL 2022. A flawless success, until re-attaching the top cap and stem bolts. I was aware that the top cap should not be much tightened, but still, I ended up overtightening it, resulting in the bolt just melting through the plastic.

A few questions:

1. A good few milimeters below the top cap, inside the steerer tube, there was something like a combined screw socket, with a hex interface up top top and a threaded interface below. I assume this is what the top cap hex bolt screws into. Would this be an expander compression plug? If it is, and its intact, could I just find any 1 1/4" top cap and screw it in here in place of the broken Canyon cap?
2. Or do I need an entirely new compression plug kit? If so, would this 50mm compression setup from PRO for 1 1/4" be appropriate for my use? Or would the 25 mm version be a better fit?
3. I may have ended up overtightening the top cap by a good bit. Could this have lead to damage elsewhere in the system? I've seen a video suggest this might damage the headset bearings.

PS: The lower headset bearing was somewhat rusty and stuck in the head tube, so it took a good bit of finnicking to get it lose. After cleaning, it turned out that it was not turning smoothly, so I guess I'll need to get a (very expensive) replacement from Canyon. This after less than 4000 km of use, only four or so rides in wet conditions, and the bike consistently being stored indoors. Am I right to be a bit disappointed in needing a replacement already?