Since the colloidal silver output limits the signal strength, am I getting any treatment through the colloidal output? Can I plugged the tens cable to out1?

Certainly you are getting a treatment, just at a reduced intensity, and yes, of course you can use OUT1 instead if you wish.

It is all about convenience. If you have the new Boost 2.0, you can use OUT1 on Boost 2.0, so you don't have to remove the Boost every time you want to use Contact mode. If you feel discomfort from too strong a power signal, then use a higher Hz.

Everyone is different as to their sensitivity but, you shouldn't ever have to be in pain when using Spooky.

Just set the parameters in Spooky2 to ensure that it doesn't go below the minimum frequency you decide to use.

I set mine, for Contact, to a minimum of 30kHz, and the software converts lower Hz to above that,and at that I never sense a signal at all, much less any pain.

For more details, please check the link:
http://www.spooky2.com/forums/viewtopic.php?f=23&t=5145