Here are my answers:
1) Do your sprayers/misters actually mist or are they more of a fine spray? I was expecting something akin to what you see in the vegetable isle in the grocery store.
Spray, and rather coarse at that. It bounces off the sides and top and goes everywhere
2) How far below the top are your sprayers located?
5 1/2 inches below the top of the 5 Gallon Bucket, 4 1/4 inches below the bottom of the neoprene collars.
3) What is the purpose of adding H2O2 (hydrogen Peroxide)?
I don't do it, I use chlorine
4) What is the proper PH level to keep the water?
I target a PH of 6.0 I am not sure how important this is since the PH strongly effects how the plants absorb nutrients, and I am just using water. But I have read several places this is optimum and if you let it stray too far it can damage the plants.
5) What steps did you take to clean the system before using?
Flush out the chips from drilling and taping the PVC before you install the spray heads so they don't clog. I let the PVC cement cure for a day and then filled the cloner with water and ran it for 24 hours. Next I changed the water and loaded it up with cuttings and started rooting.
Here is a picture of my cloner wrapped in insulation to keep the water temperature up.
As I alluded to before, I think the over heating issue completely depends on the temperature of your room. Clearly I have no problem with overheating since my room is so much cooler than the desired water temperature.
If your room is warmer than the desired water temperature, then I don't care how large the reservoir is, you are going to need cooling.
It is true that there is a small range of room temperatures, slightly less than the desired water temperature, where a large cloner with greater surface area will shed the heat from the pump, where a smaller one like a 5 gallon bucket will not. This is offset somewhat, since a larger cloner requires a larger pump that dumps more heat into the water.
Yes the 5 gallon bucket cloner is small. Mine only has 12 sites, 11 if you consider I run the cord for the pump out one of them. For me at this stage the size is perfect, and I find it extremely useful as evidenced by the fact that all my cuttings seem to be rooting just fine. I think my wife would kill me if I was rooting 64 cuttings.

Here is a picture with the lid off showing the manifold and spray nozzles

Here is a picture showing the pump and manifold

I used the ECO plus 390 GPH pump and it cost $22.42 I measured the power consumption when running in the cloner and it is drawing around 11 watts.
I spent $11.99 for 50 spray nozzles and used 9, so I have a few spares.
I spent $10.99 for 25 net-pots and collars and used 12, so again some spares.
I also spent probably $10 or $15 on PVC pipe and fittings.
I already had the 10-24 tap and hole saw required to complete the cloner. You are probably looking at $25 more if you need to purchase those items.
I don't think you should build the cloner to save money. If you add up the parts / tools, and pay yourself anything for your time, you can buy one cheaper. You should build one if it sounds like fun, and you like having stuff you built!
Dan