Firstly I would say, revert to a backup.
Then, never use PHPMyAdmin to edit posts, in fact, uninstall PHPMyAdmin, and use a tool like mysql workbench or query browser
Finally, never use youtube embed codes, to correctly embed a youtube video, put the URL to that video in your post on its own line ( just the URL, make sure it is not a hyperlink ), then save. When viewed on the frontend, the user will not see the youtube URL, they will see a youtube embed autogenerated by the OEmbed API.
For your infinite redirect loop I will need more information, including examples, and a readout of the meta for an example post with its associated URL, and desired redirected URL