I think I have it!
The message means
"you couldn't handle the truth"
which would seem to indicate that your favorite movie is
A Few Good Men (in which "you can't handle the truth!")
Thought process, building off Kevin Rock's and Beastly Gerbil's ideas:
The "five-membered syndicate" are probably
the five vowels, A E I O U, in reference to a previous Puzzling.SE question
The "unlucky one" could be
the unlucky number 13 = ROT-13 cipher.
Applying this to the ciphertext gives the extremely vowel-heavy "mue eatcat o itsiutop".
However, in the puzzle about the vowels, the "unlucky" victim is Y.
"True and trustworthy friend"
"Speak that which is dead" could
refer to Latin, the most famous dead language.
A E I O U in ROT-13 are N R V B H. Adding these into the ROT-13'd text can create some valid Latin words: mue → muner[a] "duty", eat → erat "was", for example. But this is a bit of a stretch.
Unusual features of the text:
There's a space after the ciphertext but within the quotes.
The second line mentions the "5 membered-syndicate", not the "5-membered syndicate".
The last line has an incorrect - (hyphen) instead of an – (en-dash). This wouldn't normally be notable, but there is a proper en-dash in the first line.
The last line also has an extra capitalized O.
The two "Ones" likely mean a number somehow, but this could be 2, 11, 7 (5+1+1)...
Regarding the first hint (interpretation debunked by OP):
In a cryptic crossword, (3, 4) would be "a three-letter word followed by a four-letter word". My guess is that the 5-membered syndicate clue gives XXXXX XXXXXXXXX, the unlucky one gives XXXXX XXXXX, the true and trustworthy friend gives X, and that which is dead indicates how all those words should be put together or interpreted.
We also know that one and only one of the first three clues fits the strict definition of a cryptic, due to the tag discussion on the question. None seem to contain the usual clue words, however.
Regarding the first hint (new hypothesis):
As Lukas Rotter pointed out, 1, 5, and 9 are the indices of A, E, and I in the alphabet (N, R, V in ROT13). So let's add these in.
murev eratcart non itsiutop?
These look like reversed words! potuisti non tractare verum
Potuisti is "you were able", non is "not", tractare is "to handle", verum is "a true thing".
So perhaps: "you couldn't handle the truth"? This is stretching the meaning of verum ("truth" would really be veritas), but it fits the theme of a famous movie reference.