Your numbers seem to be about as good as it can get. My average is 77 and I f**k up putts all the time. I probably leave 4-5 birdie putts out there each round. I just don't have the discipline to stop the meter right on the line for putting. ON Kiwawh my avg is probably 2-3 over par. I hate playing BPB because I can't hit half the greens in regulation.
I do think you have room to improve. Driving won't help...you'll get an extra 20 yards max. What you really need, like me, is a putter that is extremely forgiving and accurate, along with the need to have a top notch short game.
Most posts I've read suggests upgrading the putter first. The most expensive one is 600 points but I read is the best putter out there - bar none!
I personally have resisted, thus far, paying to upgrade my clubs. It won't win you tournaments (and that's where the money is) but only move you closer to the leaders. And that will make you want to purchase additional equipment, and next thing you know you have spent $40 on a computer game that only provides you a few courses. I think WGT is in a bind because they want this to take off but probably haven't realized the monetary gains yet.
Lastly, doesn't it appear next to impossible to post these ridiculously low scores on one-time tournaments? A Masters player going 15 under on BPB? I just don't believe it and think there must be some cheating going on or that player works for the company.