The poison damage from the Spiderkissed weapon is a power, which the text that you just quoted states that you must forgo when using the bonuses of the Ki Focus. It's an either/or proposition, not a Chinese buffet.
I disagree that your refutation is valid. My proposition is that I am not using the power of a spiderkissed or a paired weapon when I'm making an attack with it. I've already used the power, and that action to use the power is over. Can you explain how I am using the power of the paired weapon or spiderkissed weapon when I am making an attack, yet I'm performing no action to
use these powers. As you said, I can only
use the powers and properties of the ki focus when I'm making an attack that's enhanced by it. You are not addressing the point of my argument, you're stonewalling.
A possible counter argument would be as follows:
1. Through an interpretation of grammar, "using a power" includes: "utilizing the effects of a power AND performing the power as an action."
2. An interpretation of powers, properties, and items: The only way items can be modified is through gaining powers, properties, or enhancements, so any modification to a weapon is one of these. When the spiderkissed or paired weapon powers activate, they're giving those items a property of dealing poison damage or 'exsisting in a pair'.
3. This effect is not within the spirit of the rules, so it should be overriden by a DM.