I have in the past worked out a L/D for the B757 at around 20:1, so that tallies with your figures (I am pleased to say)! Never took the time to work it out for the A321, but would imagine with some decent winglets it must be a bit higher.
Regarding deck angle, I've often wondered when pushing a trolley from back to front whether there is an incline to the wing root then it goes down hill towards the cockpit?! There has to be a bending moment in the fuselage, certainly on the longer fuselages.