Can you get an STD any other way than being sexually active? For example using a dirty bathroom or scratching yourself down there over top clothes

Sexually transmitted. disease, by definition, is sexually transmitted. You can contract infections that can be spread by other means as well as by sexual contact. For example, you can get AIDS or hepatitis from sexual contact or from blood transfusions. You cannot get STD from dirty bathroom or scratching.
Nope, urban myth. Over the centuries, people have claimed to have caught STDs nonsexually -- toilet seats, shared towels, etc. But these are only face-saving excuses. A recent article in Marie Claire "warned" people about STDs from tanning beds, shared towels, etc. It's all BS; any exceptions are so rare they can and should be ignored. Avoid unprotected sex with new or unknown partners and otherwise don't worry.