I think those numbers are wrong, unless you are already at a very low body fat level (which you might not be since you are cuting???)
Lets see: It you are 173 lbs and your BMR is 1908 cals, means your LBM is 156 pounds, which leaves 17 pounds fat... that would be the same as saying you are currently 10.89% BF . How does that sound? Do you look 11% body fat? (this is already VERY lean).
If it doesn't look like it, I would recommend you get your body fat tested (any method would do) so you can get at least a ball park figure. The BMR calculation based on body circunference or worse, only weight, etc is very vague and based on statistics.
On the other side, with that much cardio, you need to increase your weight training days at least to 4 times/week.
for a 173 lbs gus, wanting to cut, I can say that 2100 seems high, unless you are really 11% body fat. It all depends on the amount of muscle you have already. Only that defines your metabolic rate.