Full into work right now.
I have started parsing the players totals, finding the missing category points, and it's going splendidly. I have found most of all, and have parsed over 50 low ranked players. I have found how ATP decided to categorize tournaments, and if some of the tournaments followed the exact GP rank, some didn't. Queen's for instance was categorized as a D (which is usually for 50K tournaments, despite GP's C, which is for 25K).
A few constants for these first rankings:
1. 1972 was not counted at all.
2. European Circuit not counted.
3. Salisbury counted as D, Hampton as F (or at least what I figured until now).
4. There are errors, many players didn't count Berlin, but there are some who did, so this might be a miss.
5. The B category, which included Rome and Las Vegas more than likely was superior to C (75K), unlike D is to E (they award the same amount of points, except R32). What I have until now, B class awards 4 points instead of 3 for R16.
6. I have found that TC awarded 1p for R64, 3p for R32 and 5p for R16.
Will continue this in the weekend if I have time, or more than likely on Monday.
Thanks a million once again, Markus. That was a brilliant piece of information.