As far as making them grow slower, there isn't much you can do about it. With all that calcium supplementation the cham probably won't get mbd. But, underfeeding would be more of a cause of mbd than overfeeding. As long as they have the nutrients, they'll grow healthily into beautiful, large adults. This subject has been touched here before but was pretty controversial, if i remember correctly.
Your temps and humidity are good, and be sure those temps are 70-80 for the ambient temp, and 90-95 for the basking spot (change the bulb to a lower wattage if the ambient temp is highger, say in the summertime). Four mistings a day really isn't necessary, one in the morning and one about an hour before lights out is fine. Dripper is good, but some chams (including two of mine) don't drink from them, although it is good to try, so please do.
A cham is an "adult" when it refuses to eat more than the usual juvenile diet of up to 20 crickets a day. This being said, refusing to eat can also be very bad. I should say, I guess, when the cham is eating much much less, but is still ehalthy in every other way, is at or is near the proposed adult size of the species, and they are a bit over 8 months old, then the cham won't be doing any more growing.
Don't supplement every day, this can cause huge overdoses of calcium and D3, which can lead to kidney stones/kindey failure. For a juvi, every two days is fine. The multivitamin can be used every 2 weeks. When adults, the supplement should be used MAXIMUM every three feedings, and multivitamin MAX every 3 weeks, even every month if you gutload the crickets and other feeders properly (be sure to read up about gutloading before you get your cham).
I think that's everything...oh well good luck with your cham!
(be sure to have a properly sized all-screen cage with REAL plants, fake ones are good additions but real ones are so much better, and cheaper!). AS for lighting, I don't remember you mentioning it, so you should have a normal house bulb of proper wattage (60-75 watts if the temp is 70-75 in the air) in a reflector lamp, and you should have a UVB light of some type, like Reptiglo or Reptisun 8.0's.