Sorry about the very late reply...
If you are still in need of info, Fluted and flat is kind of a sweet spot for the deck setup, you want some wind to throw the grass but not too much it blocks up the deck, if that makes sense? you can fit 4 fluted if you intended to catch or 4 flat if you only wanted to slash/mulch.
Brake pads are fibrous, couldn't tell you what they are made of.. that one looks fine? but they should only be held on by 2 pop rivets,
The chain is only there so if you lift it up to say load it onto a trailer, it wont droop right down and be a nuisance. just make it long enough so it is loose at the lowest cutting level. it isn't really even necessary most of the time.
