Dimming mode is best for most heat sources - perfect. It's doing exactly what it should be doing under dimming mode - only giving the proper amount of power necessary to keep your heat source at the temperature you have it set at. The power strip probably isn't turning completely off, but going below a level to support the light being on (I assume that's how you're seeing that it's going off). Do you have anything else plugged into that power strip? If not, a plain ole extension cord will work and you can save that strip to use elsewhere.
Here's a link to the Herpstat User's Manual: http://www.spyderrobotics.com/manual...t12_manual.pdf.. The section on Safety Setup is on the second to last page. The setting you have it on is the default setting, but there are other options should you choose to use them.
What you're doing with the 2nd probe is basically turning it into a thermometer (a really expensive one). The reason it reads maximum power is that the temperature setting you have that probe set to is higher than the temperature it's reading. It's trying to heat something and not being successful because there's nothing plugged in. If you want to use it this way, you could turn that probe's temp down as low as it'll go (hopefully well below room temp) and it won't try to send power to that output anymore. If you're not powering a heat source through the second port, it doesn't matter what heat setting it's on (dimming, on/off, etc).
You're very welcome!