You are going to have to elaborate how it is kicking your ass. Are you just out of breath, or are your arms, legs, or back tired as well?
My first suggestion is to just slow down. My wife goes too fast all the time and she claims that she can't slow down, but you can.
The performance readouts on the machines are a little misleading, because the whole point of rowing is efficiency. You want to go as fast as possible while expending the least amount of effort.
The proper sequence to rowing is Legs - Back - Arms for the stroke, and then Arms - Back - Legs on the return. If you were competing and you pushed as hard as you could with your legs, there is no way that your arms wouldn't be stretched straight. If you were rotated 90 degrees and lifting a box, this would be the exact wrong way to lift, but it works here.
Try to make your return take twice as long as your stroke. Learn to relax during the return. Your heart muscle spends just over half of its time resting, don't think you can do better than that with your puny arms.
I usually row between 18-20 strokes/min. Of course, I am on the taller side, but you shouldn't be over 25/min unless you are really short. If your stroke rate is really high, you are probably using your arms too much and your legs/back not enough. Learn to stretch forward as much as possible at the catch.
<---- Former rower who still owns/uses a rowing machine