They actually have "circuit training" in etools - I've never been to curves but I've always assumed it was that kind of thing. Mixing/alternating strength training and cardio stations with minimal rest. But WW's values for circuit training are... pretty generous! 30 mins of circuit training gives me 8 AP.
If you think your heart rate isn't getting too high, that's definitely overcompensating on AP's.
I am probably just not understanding the idea of Curves - amazing that they are everywhere but if you haven't done it it's a big mystery.
You mentioned doing it 6 days a week - are you alternating days for upper body/lower body strength training or am I just wrong in thinking there's strength training in there? Cause when I think of strength training, like yesterday I was at the gym doing lat pulldowns, bench dips, blahblah, I wouldn't want to go back today and do those again, I need a day to recover.
Also wow that sounds like a great deal on a treadmill!