That's not what the bit I quoted says!
ATP site also says "Commitment players (top 30 in 2012 year-end ranking) can count their best six (6) results from ATP World Tour 500, ATP World Tour 250 and other events (Challengers, Futures, Davis Cup, Olympics) toward their ranking. To count their best six (6), players must have fulfilled their commitment to 500 events - 4 total per year (at least 1 after the US Open)."
I agree it's vague but i'll roll with it, so he needs 4x 500 events
He's confirmed for:
Barcelona & Tokyo which is 2
Monte carlo is included so that's 3
The rest is sketchy, if he decides to play davis cup after the US open i think this can qualify as a 500 event
"If a player doesn't play enough ATP 500 events and does not have an ATP 250 or Challenger appearance with a better result, the Davis Cup is counted in the 500's table"
But unsure wether you have to play for a team in the world group to qualify.
I don't think it will be Hamburg as that is clay and just after Wimbledon, Washington as it's OH hard and at the end of July so he will have had the break after Wimbledon but that would mean 3 back to back tournaments before the US open.
Basel would be the best bet but i wouldn't count on it, if you look at his schedule for 2013 there is only the 3 500 events he has so far signed on for including Monte Carlo so my guess is that he just decided to dump Dubai and get a big fat 0 points as a penalty.