Brainless? I don't know about that, they have a Dominant Ti function.
Yes. Intellectually they are very bright people, but their urgency to be in the moment can land them into unnecessary trouble. I.E. Hot stranger seduces ISTP. ISTP jumps in without any forethought. ISTP later finds out, they contracted an STD from the one night stand.
Hmmm, I don't know about the INTJ one. If you say the right thing I will be tremendously affected. I might react by overly expressing it, or repressing it to an extreme. How about "stubborn." I feel that's a better word.