Re: How do i know when i can feel KI?
Chances are, you've already felt it, you just used a different word.
In Japanese, 気 is used in hundreds of different words, mostly having to do with mood, energy, spirit, stuff like that. If you've stood on a cliff overlooking the ocean and filled your lungs with the clean, salt air, you've "experienced" 気 in a way that a Japanese person would recognize.
In the aikido context, it can be a useful shorthand for describing a variety of physical phenomena having to do with attention, body structure, and mental focus. It can also be a mechanism for collective self-delusion. If you find it useful, great. Just make sure that your stuff still works on people who don't feel "it" when you wave your fingers at them.