I have added answers to each of your linked issues.
I believe something has gone wrong with the way you upgraded to 2.7.13. The screenshot you posted here: https://answers.atlassian.com/questions/57766/fisheye-w-jira-user-database-problem-communicating-with-crowd?page=1 is for example not from fisheye 2.7.13.
To downgrade from 2.7.13, you will have to do a restore from a backup. However I think if you can work out why the install appears to have gone wrong you may be better off.
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