1. You've got it, about the top of the guide roller block needing to be square to the blade at least in front elevation for the scraper to work correctly. File off, turn by holding in the lathe independent 4-jaw or shim are ways to correct.

2. You can use any design for vertical table that appeals to you.? I used the small angled-shape table as an example because it would be easy to incorporate into the scraper block design than the flip up one but do as you please.? At the moment I have to dismount the scraper to bolt on the vertical table so combining the 2 has real-world advantages

3. I thought you did mean printing the scraper blades as one with the body and can see no real reason not to? other than longevity,? PET doesn't have the same abrasion resistance as UHMWPE, but that said it might well last long enough. HSS hacksaw blade ends obviously would last longer than any plastic wiper/scraper and I like the idea of slots for them to fit into.? The only trouble I had in making the aluminium version was tapping the threads for the fixing screws, had to grind off the bottom of the tap, so the threads would go in far enough - there's not much room for the end of the tap with the threads angled to one another.? Maybe you could print the threads? (- only just thought of that and don't even know if its possible???) I'm trying to envisage the press fit of the nuts but there really is very little room to slide 2 nuts in the back of the blade holder

Give it a go! - jv