Interior linemen often don't "give up" high numbers of sacks due to how most places account for them. They typically only put the sack on the linemen if they are engaged with the defender. I don't believe that any site credits any of Dallas' interior linemen with more than 3 allowed.
Look at some of the numbers floating around this site. Pettiti 13.5, Tucker 12.5, Allen 2.5, Johnson 1.5, Rivera 2.75 are all pretty common numbers. I don't remember an approximation for Adams off the top of my head but it was only a couple. Now those numbers only add up to 32.75. Do you really believe that TEs, RBs and Adams were responsible for the other 16? If that's the case, the line's fine and those areas need addressed.
Allen only engages a defender if the defender engages Allen if that makes any sense. Unless there's a player lined head up on him who fires into him, he doesn't block anyone in pass protection. I saw it a half dozen times in the Pro Bowl alone. Pick any quarter of any Dallas game this year and rewatch it. You'll see what I'm talking about, Allen in space at the line, head turned watching someone get blown up in the backfield.
What's worse, the player who attempts to block someone and fails, getting the "sack allowed" or the player who stands there and watches it happen?