He will need probably between 50 to 70 points in the final two American challengers to get in directly, which probably translates into 2 SFs at least, taking into account the subtraction of his 17th and 18th results. It will be tough, but he can make it easy on himself if he just wins one of the challengers, no big deal
Also, to sokk, I know you seem to think he skipped the challenger tour, but he was in 12 challengers this year. He had 3 SFs, 6 QFs, 1 R16 and 2 R32. That seems like a lot of success to me, and he could try the next stage with results like that.