Sperm won't live for more than 2 minutes on anything like tissue, your skin or your sheets. It'll only live for 48 hours inside a woman!
Sperm is very fragile and it will be killed if you do anything. Hell, it'll die even if you don't clean your hands! Don't worry man!
About the porn thing...it's your choice. It's against the law, but many people on this site watch porn underage. It's up to you whether it's right or not