If you used a 7mbps fixed (CBR?) bitrate, how come it never exceeds 6.5mbps in your bitrate viewer?
Using LPCM audio, you have your total video+audio bitrate at dangerous (imho) levels (either 8mbps or 8.5mbps depending on if it really was 6.5 or 7mbps encoding).
Were the 100 discs duplicated (burned) or replicated (stamped)?
Also, your total disc usage is well under 1gb — this has caused folks problems in the past, and they fixed it by adding a folder with some “dummy” data to bring the total disc size over 1gb.
Keep your total bitrate at/under ~7mbps — I would try using Dolby Digital audio instead of LPCM.
George