#1, yes, and yes its ugly. A milled one stamped LB shouldnt be hard to find if it bothers you.

#3, I'd have suspected the beech as original, walnut for early british made ww2 and pre-ww2 guns (others know more than me on that)

Its likely lots of parts have been swapped in and out over the decades so whats original and telling what isnt is a hard game IMHO.