I'll make Gregory's comment into an answer:

You don't owe anyone anything. Just announce that you'll be leaving as of X date so nobody gets caught by surprise. 

The circumstances and details of you leaving and are your business and your business only. 

You can give more details in a private setting to friends and colleagues you trust, but only as much as you feel comfortable giving - again, you don't owe anyone anything and they don't "have a right to know" anything beyond your last day with the company and *maybe* knowledge transfer.

Find another job and move on.

The other concerns can be addressed to HR during your exit interview (if there is such a practice in place), or another company defined communication channel.