You are right to be concerned about losing your vault data. Reinstalling the ID Safe on your PC can will not affect the actual cloud vault. There seems to be some issue with the IOS version of ID Safe.
What is your phone's version of the IOS operating system? There is another user here that is having trouble with IOS 10, that I am not seeing on IOS 9. https://community.norton.com/en/forums/norton-id-safe-ios
Not sure if these two issues are related.