I can't spell PHP, much less program in it! I took someone else's plugins and modified them for Events 1.4. I used then successfully to convert one site more than a year ago and haven't touched them since. I forgot that I had them. Good luck!
When the dust settles for you, you need to look for a good backup component for your site. There are a bunch that will do the database only, and a couple that will do the entire site. I have only ever lost a site by my own hand, but I was glad that I had the backup.
These core database tables are way outside my area of expertise, but look at jos_core_acl_aro and jos_core_acl_groups_aro_map. I think you need the corresponding records for your users in those two. That defines their group level - SA, administrator, manager, author, etc.