Removing najaasat

Q: 

  1. My question is that after intercourse I wipe myself. If some sperm gets on my hand I wipe it with a tissue then put my qamees on. Is my qamees paak or do I have to wash my hands before touching anything.
  2. If something is najis. Do you have to wash it 3 times and squeeze each time or until there is no sign of najasaat?

Changing one's zakaat date

Q: I have always had my Zakaat anniversary as the 15 of Ramadaan. If I wish to change this date is it possible? Let's say I wish to from next year change my year to 15 Shabaan. I will do all my calculation on that date and give Zakaat at 2.5%. Is this possible? Alternatively, if the date I wish to use in future is 15 Shawaal, how would I put this into effect? Bearing in mind that this will then make it a 13 month year.