First of all there is no data based on marks for AIIMS admision, so can cannot say for sure how much to score as it changes every year and even with exam shift- morning or afternoon. Secondly, there is no pattern in admisions of PwD as many a times the seats go vacant and is shifted to respective categories.

However, based on my personal experience in AIIMS, I would say a rank below 2000 is safe enough to get you a seat in AIIMS through PwD category.