It may be too late, but it's been my experience that the outlet of the float should be over the water level. I forgot why I do that, but it works well for me. Maybe it was a snail creeping under it.

When I had my kalk gravity fed ATO, I had a lot of paste building up on the bottom. I even put a pump in there to constantly stir the mix. but I could never figure out how much to put in there.

Now it's two scoops in a quart container, vigorously shaken and deposited directly over the inlet to the return pump. Clouds the display for a few moments.

If I ever went back to an automatic system I would deposit it in the same location.

I put it all in there, I don't worry about the paste that develops at the bottom when it is allowed to settle.

I had dosed originally in the water in section of the sump (rubble rock), but decided that the ph swing in that area would be too extreme for the purpose intended in that area.