Exporting project for DCP conforming: no idea what producers are talking about!

Hi,

Just finished the 15 seconds ad that was supposed to be screened on TV, but, I've just learnt, will now also be shown on local cinemas.

So, as a result, apart from going from 25P to true 24P and from rec709 to DCI P3, the guys that will take care of the DCP encoding have a few demands:

1. - Images en tga ou tiff ou DPX(10bits) en RVB,
2. - Son en 5.1 : à 48 Khz à 24bits, à 85 dB Leq(M)

Ok, so First question: If I export my project which is rec-709 16-235 in RVB Files, how do I know what happens to my levels? I mean TIFF is 8bit 0-255.  SO I fear my black will get washed out and my whites soft grey. Does that make sense? Second question: what kind of "weird-i've-never-heard-about monkey" is 85DB Leq(M) and how do I conform to that. I mean I'm used to calibrating our screening room, so soft-calibrating speakers to 85db with measurement mics and all is a no brainer, but is that the same animal at all?  And how do I calibrate my Avid audio to that? thanx for shedding some light if you can.