Pardon belated comment from a complete stranger, but one suggestion might be to put an 'author's notes' thing at the end where you credit the particular speeches, if they are few enough to do so? Sort of, "Bob's comments about the ineffable nature of trees were quoted from This Film" or whatever? If there are too many/too short quotes for this to be sensible, just a blanket thing in the disclaimer of "there are several direct quotations from This Film throughout the fic, which are solely intended as a tribute and I make no claim to them blahdiblah..." I think the main issue with plagiarism (cf Cassie Clare) is when the author passes off stuff as her own, or just allows other people to think it's hers and takes the praise without disclaimer, which you clearly aren't trying to do, so it sounds fine to me. Burntcopper's rant sounds less about the plagiarism issue per se, to me, than just about fic ending up as rather boring and pointless!