The only "problem" I see is that a 1515 may be too heavy, race wise. I believe there is no such thing as too powerful, it just requires more driving practice.
About the 100A rating on the motor, you aren't going to be drawing 2200 watts from your batteries ALL THE TIME. That is mainly a peak rating that you see upon acceleration. Though if you have it geared for 120 mph, then you might see it continuously. At lower speeds, say 40 mph, you will only use about 30-50A continuously.