I would not run the effluent into a skimmer. I don't think that it will serve any benefit or be harmful. Then again, I never tried to see it the skimmer would lower the Alk or Ca- shouldn't, but I don't know. You would run your effluent at the tip of your output for your skimmer if you wanted to put in on there some way. That would just keep your effluent in a high flow area.
Instead of counting the drops per minute or second, you could collect all the effluent over a period of time, measure the pH/Alk/Ca in the effluent and use that to adjust the rate, pH, etc. There are several ways to adjust it. As long as you know the basics about how it works. Make sure to make suttle changes and check frequently while you are establishing a baseline.
I would not go above 12 for Alk. I don't go above 9. There are several people who are succesful at keeping high Alk, I am not, and I have seen the negative effects of high and low Alk. The 450 Ca is fine.