Impurities on the body

Q: In Europe leather men shoes have leather sole. Mostly this leather is from pork-leather since the sole has to be soft, and being soft is one of characteristic of pork-leather. Now it is that most Muslim buy such shoes and wear them. My question is since these shoes are commonly worn and we do not know exactly who wears them only that is very common, how should our behavior be in the rows of Salaah since people do stand feet to feet. Their socks do they become impure by wearing the shoes as inside the shoe there will some humidity after all, and people do touch each other with their feet i.e with the socks. Since this is a matter of Umoom al Balwaa what is the view of the Ulamaa on this issiue?

Q: If one gets 1 drop of urine on his knee, does the skin become pure by wiping the drop away with a dry tissue and thereafter wiping the skin with a wetted tissue ?

Q: If one touches with ones hand or clothes for example a pigskin leather jacket, does his hand/clothes become impure? If one is praying and someone joins the saff who is wearing a pigskin leather jacket, and during the Salaah the pigskin leather jacket does touch the person for a duration of one rukun does his Salaah become nullified?

Q: If a dry napaak hand is rubbed on a dry carpet and someone subsequently performs wudhu and walks with wet feet in that area, does that area of that carpet and that persons feet remain paak for the purposes of Salah?

Q: If a person walks with wet feet on a dry impure carpet, does his feet become impure?

Q: If the clothing of a person, or a part of his bare body (such as his hand) or his khuff, touches an impure place which is dry, does it make it impure? For example, there was some urine on the carpet, and then it dried totally. If the above-mentioned things touch it, do they become impure?

Q: A lady is old and wears a napkin. It is difficult for her to walk and needs to have assistance. If her napkin becomes wet often, does she need to go to the toilet as well as change that napkin every time? It is very difficult for her. She cannot do any of these things by herself and needs for it to be done for her.