First, thank you so much for assembling all this information in one place. You have saved me no telling how many hours combing the web for information. I'm going forward with flushing the copper sulfate, as it has been proven to not harm the bacteria in the tank when done properly. I am going to see about the tee for anything else I need to do and later the risers. Is it just gravity that makes liquid poured into the tee not flow back to the tank? In your photo it looks like you would have to pour extremely slow to keep some liquid from washing back.
One more thing confuses me. We should use peroxide/oxy-whatever to get oxygen in the drain field. You tried to find a way to oxygenate your tank. Would the same chemicals we use to oxygenate our drain fields not be beneficial to the bacteria in the tank as well, or is there some difference in the microbes there vs the drain field?
Thanks so much for your input.