For your queries
- DoS and InterPlanetary Storm Malware
- End to End Integrity.
- Confidentiality and availability can be addressed by following certain security protocols depending on your requirements.
- Only DDOS and Storm Malware but can be avoided using certain protocols.
- For malicious purposes? Not sure Or Not that I know of.
- Privacy cannot be guaranteed with any platform which you are using online.
- There are several threads related to this one
IPNS Signature Authentication - Just answered by @RubenKelevra