Locked out of the admin interface
I don't have enough rep to comment, but I can answer a few of your questions.

Craft logs are located in /craft/storage/runtime/logs.

Make sure you have a backup of the database before you uninstall the plugins. Depending on the plugin you could experience data loss.
To remove the plugins you can go to the /craft/plugins directory and delete the folders. 

Keep in mind if you do this it will not allow the plugin to clean up after itself. 

I also found this which may help avoid the clean up issue. https://github.com/khalwat/uninstall. It is a tool that allows you to uninstall plugins via the cli.