Beginning on November 7th of last year, I initiated a diet based on low fat intake, moderate-high carbohydrate intake, and moderate protein intake. The following picture is a composite average of my daily nutrition and exercise habits, which consist of racquetball and weight training.

I'm 5'10". At the beginning of this diet, I weighed in at 244 pounds, with high body fat but moderately muscled. At my most recent weigh in two days ago, I now weigh 214 pounds.
My basal metabolic rate is approximately 2100 calories, so I restricted my diet to around 1600-1700 calories (the image is somewhat skewed by days with only partial entries, so some 900 calorie days drag the average down). This is a sound reduction, but I've been concerned that on days when I play racquetball and train, I'm getting a very inadequate amount of nutrients. I burn upwards of 3100 per day on training days (about 4 per week), as shown in the graph.
My question is, despite my continuing and effective weight loss, which has not been accompanied by muscle performance decreases in the gym, am I risking my long-term weight loss by eating too little? Do I need to gradually increase my daily intake to around 2500 calories to keep up?
Thanks for any help, and I can answer any additional questions about my diet or training.