Jimbo, if the fish kills are happening yearly, I'd worry about how to fix that issue before worrying about forage. Believe it or not a SMB only pond can do fine by itself and if there are other critters they'd do okay. (I know Dr. Dave Willis can speak to this more as he's written about it)
The fish kill is the issue. Fish just don't die every year en mass. (well, they're not supposed to anyway) Especially if it's happening yearly. You mention no fish over 1/2 pound in 7 years. Was it about 10 years ago that you put the smallies in? Have you had a fish kill every year? What time of year? (always july-aug?_ I'm assuming no aeration? (can you run an aerator to the pond?) Is there lots of vegetation? Do you know what color the water is when the fish die? Other times of the year? If it's low DO and you fish kill every year adding other species will only complicate the problem.
