Outlook 2011 cannot rebuild – clear steps to resolve please

Last night outlook 2011 (14.3.5, 52MB) prompted me to rebuild database, dutifully did so (without first duplicating) and seemed to work.

This morning the prompt reappeared and resulted in a 'database could not be rebuilt' message and error code 20997 (from memory). I am currently not able to open Outlook.

As suggested here I deleted Library preferences mentioning database utility and daemon, no joy.

I created a new identity and Outlook opened normally.

My email is IMAP so inbox and subfolders safe and sound on host website.

It seems i'm going to have to create & build a new identity and transfer my contacts, calendars and notes across, none of which I can afford to lose. My Time Machine hadn't been working properly for the around 3 weeks so not sure I can utilise but let me know otherwise.

Please advise on how to do this in a simple (for a non tech literate) and safe way that will not jeopardise contacts and calendar in particular.

And how to avoid it happening again.  

Thanks