If you hunt around a bit, you can find a previous thread where I explained in detail how to "dial in" a reactor. There's also an article that's bookmarked in that thread. Basically, you should not try to raise your calcium that much with the reactor; use calcium chloride and sodium bicarbonate (baking soda) to bring up the calcium and carbonate. Use a salifert test kit to measure your ca and dkh levels; some other kits vary wildly.

The "bubbles/sec" measurement is kind of useless as an absolute, because bubbles are different sizes. You can use it as a comparison, though, and you use a ph probe to test effluent ph. That's how you set your CO2. 6.5 is a very low reactor ph; I'd go more like 6.7; depends on what kind of media you're using. ARM can run at a slightly higher ph than crushed coral as a reactor media. As far as effluent flow; I have no idea what 13gph is, or how eleyan got that number. You can start with a steady drip, like a drop or two every second. Try to find that previous thread, it'll explain the whole thing. Of course, this all depends on how big your reactor is, what kind of calcium drain you have, etc.

BTW, if you're setting up a reef tank, I'd strongly suggest removing the crushed coral substrate from the tank. Use a fine grain sand instead, like Southdown or Pure Caribbean. There are all sort sof reasons for this.