1. Get the WoS Address (looks like an email) . Then on your edit profile (depends on your client) paste it in the LNURL or lud16 section 

2. Not necessarily but using an extension like alby or nos2x makes it much safer to use new nostr  WebApps. 

3. Not sure, if it's a chromium or Firefox fork  browser you should still be able to use it. Does duckduckbrowser not have extensions?