I use Iphoto in the following way which may suit you better. Iphoto is a great app.
I always drag photos from my SD cards using Finder into "proper" folders under Pictures in the file structure. My iphoto never sees my SD card!
I then go into iphoto and "import into library the folder in my Pictures files. Iphoto then uses the folder names as "events".
If the folder has been imported before, because I have only added photos to the existing folder, iphoto creates another event of the same name. I then highlight the two events, right click and hit Merge Events. BAck to one event = one real folder.
If I use iphoto to make small corrective edits, I always immediately Export the "Current" version back to the proper folder in the file system with a suffix. That way I don't have to worry about where the heck iphoto has stored the edited version.
If I get tired of the wasted space in the iphoto library I find it and delete it, then import the whole folder structure fresh into iphoto.
By the way I unticked that Importing [] Copy to the iphoto library in advanced preferences.