Firstly, when you created the owner group and had it inherit permissions from superadmin, all of the permissions in your owner group are reflected in the superadmin group-- therefore, if you remove accesses from superadmin, then it removes them from owner too. If you want to delete your superadmin group entirely and keep the permissions in a higher group, you'll have to grant access to each command ON TOP of the access inherited from superadmin (this can be done by right-clicking on a permission that has a grayed out checkbox, and then click "Grant access on top of <inherited group>").
To give you back your access to these commands, you must use the following command from the server console:
ulx groupallow owner "ulx groupallow"
Alternatively, you can reset all of the groups to default, which you can do by deleting the garrysmod/data/ulib/groups.txt file (and maybe the garrysmod/data/ulib/users.txt file if you need to reset the users too), then complete a changelevel.
Also, it's really not recommended to delete your superadmin group because I believe some non-ULX addons only check the admin and superadmin groups for access, so those could break. Plus you don't have to mess with permissions as much if you keep it
EDIT: Ninja'd!