I shoot 3 under. I adjusted the tiller to where the bottom limb is 7 3/8 and the top limb is 7 5/8. Is that right? Or should I just bottom out the limbs to be equal?

Even tiller is the standard for 3 under but, some like a little positive tiller. Your bow will shoot just fine where you have it set, but I would even them out to start with and then adjust from there. Tiller, without bow sights, is more about the way the shot "feels" than anything else, with bowsights, it is a way to adjust to stabilize the sight picture. It's alright to play around with tiller, since you're going to get the average of both limbs anyway, no matter how you set it, but many say, "set it and forget it".