Most nutritionists recommend a maximum calorie deficit of 1000/day. And most people create a calorie deficit through a combination of exercise AND watching their intake.
It is perfectly possible to create a significant calorie deficit through nutrition alone.
A guy your size is likely burning over 2500 calories per day through your metabolism alone.
Also, take a look at Spark's Limited Mobility lifestyle center for seated workout ideas. www.sparkpeople.com/resource/lifestyle_cen