Take time to build up on it. It used to take me around that time on Level 10 to do 2000km, now it takes me 21 mins, and I slow down a few times to glug water. I normally move at around 32-45 rpm according to the machine. I don't often row, I do alot of other cardio type workouts which I think improves my overall fitness so when I do go back to the rower I can move faster. It can be done, it just takes practice.
Maybe try speed intervals: go as fast as you can for 30 seconds, then to normal for 30 seconds to 1 minute, repeat as often as desired. Over time this will help to improve your speed.
first of all you might need to oil the chain if its been a while since you used it.
I row for a team, and when we workout on the erg, we put the damper at a 4 for almost everything. I really don't know how a damper setting of 10 feels, however it shouldn't make a 10+ minute difference from what guys your size pull (on average).
It's more important to keep track of your split time (should be one of the options on the monitor, ___ per 500m. Usually it will be somewhere from a 1:45-2:30 depending on how strong, fit, etc you are. As someone said, try interval training to improve your time.
As far as calories go, im 136 lbs and when i pull all-out for 5 minutes its about 60 calories used up. When I row moderately, it drops to 40ish.
^^obviously not completely accurate but that's what you've got to go by if your erg doesn't compute it on its own