Between the skimmate and evaporation, I'm having to add about a gallon/day

Maintaining high calcium levels

1. Between the skimmate and evaporation, I'm having to add about a gallon/day. My tank turnover is about 1200 gph on a 100 gal tank plus 30 gals in sump and probably about 5 gal in skimmer circuit. Is this amount of top off/day about right?

That sounds a little high but I wouldn't be surprised if you're possible "estimating a bit high"? My 200 gall in the middle of the summer would be at most 10 gal per week. On the other hand some people who like to maintain high calcium levels will place large fans over an open sump to accelerate evaporation... IMO on the "average tank that isn't necessary. also, if your really producing measurable skimmate chances are your skimmer is set too high. Now is the time to start putting the valve to use. Lower the water level in the reaction column so the bubbles become large, very large. It will initially seem the skimmer isn't set rite, but you want to end up with "dryish" skimmate" It should resemble thin mud. The real efficiency of a skimmer is not how much is "looks" like its foaming but rather the quality of the skimmate. Once you have the skimmer set low... and it "kicks in" you'll see! The commercial ETS setting is with no water in the reaction chamber. I run mine at about 2" of water in the reaction chamber

Will it be OK to use Kalkwasser every time?

Absolutely use all kalk for all evaporation

2. I have VHO lighting mounted inside the canopy on a hinge and chain so it can be adjusted, if needed. The tubes are about 3-4 inches above the water surface. Is this about right?

Sounds neat! Id say you want them as close as possible without getting excessive splashing. 3 - 4 does sound about rite

3. I have noticed that the skimmer can be putting out foam over the top for many hours. Then, if I add water to top off the system or even reach into the tank long enough to increase water into the sump, the reaction column collapses and it takes awhile to regain height and produce foam. Is this normal?

Absolutely, as soon as you add anything to the water a reaction takes place which affects the skimmer (tension of the water... ) nothing to worry about, but you can bet on it happening every time.

4. Snails purchased for algae conrol spend much of their time at or near the water surface. Normal? Ive never really heard that but I suppose anything is possible. Their just probably getting orientated, finding their boundaries etc. I had some trimming to do at the back of the eggcrate. I knew I dropped a few pieces behind and within seconds there they were, courteously delivered by the current to the front of the tank for easy removal. What a great concept.

Great! Im not sure if you notice it now but, if you look at the tank from the sides, you can really see the circular motion of water. In the past few years I've taken some heat from the "online reef community" e.g. usenet by folks who challenged my idea about using a raised bottom. Their claim was there was too much circulation and not enough dead spots where microfauna could flourish. I just got tired of trying to explain that our tanks are not the ocean... and really cant ever compared to a "natural" environment. I've always found that having as much control as possible as to what goes on in the tank is the best goal to have. You'll also notice over a period of time the microfauna e.g. calcareous tube worms and the like end up in the same area you fund your chip's! After a while you can let that front area "go unvaccumed" . Im glad everything's working out for you