Is it true that water that passes over the head of the penis dried with a tissue, or over impurity wiped with a tissue after urination, then this water falls on the body or clothes, is considered pure because the impurity has become حكمية (rulable/judged to be absent)?

The scholars have explicitly stated that the ruling of impurity does not transfer. Thus, if the physical impurity itself is removed, whatever comes into contact with its former location does not become impure, nor does water that separates after the removal of the impurity cause whatever it touches to become impure. Therefore, your understanding is correct.

If you used tissues to remove the impurity, you are not obligated to use water afterward. Some scholars are of the opinion that removing impurity by any means is considered a valid removal of its ruling.

We also alert you that excessive scrutiny in such matters can lead to waswasah (obsessive whispering/doubt).