So for supplements, you should probably buy some Rep-Cal. Supplements are a fine powder that you lightly dust on feeders so that your chameleon can get all of its vitamins/calcium/nutrients required to be healthy. You should buy a supplement without phosphorus, and I believe Rep-Cal is a brand that does not have phosphorus. You should use regular calcium dust without Vitamin D3 every feeding, and then twice or three times a month dust the feeders using a calcium with Vitamin D3. If this is confusing, I can explain it better with examples if you need it.
I suggest you buy an automatic misting system. Mist King is probably the best brand, but I have been using a Monsoon for the past year and a half and had no trouble. But I suggest you buy the system that works best for you and your chameleon. A misting system will ensure that your chameleon gets the chance to drink water even if you are not with him.
Gutloading is a very important component of feeding chameleons. It is when you feed the insects that your chameleon eats with specific ingredients that enrich the diet. I have a list of good gutloading ingredients here:
Gutloading Ingredients
For example, you can give your crickets something from the list the night before and then the next day they will have tummies full of goodness, which your chameleon will benefit from. how are you housing your crickets?
I am not entirely well-versed in Jackson's chameleons, but I am fairly sure that you should upgrade to at least a large cage (of the Reptibreeze standards) by the time your chameleon is an adult.
Are your thermometers digital or analog? If they are analog, you may want to switch to digital because the digital thermometers (and humidity gauges) are more reliable and will most likely last longer.
He is quite cute, and apparently going through a shed! Make sure to give him some extra misting when he sheds so that he has nice healthy skin once he is finished. Age is always hard to gauge because it entirely depends on the chameleon and its livings conditions, as well as its species and ancestry.
Can you please post a picture of his tail and under his tail? Just to check for the hemi-penal bulge to signify that it is a male.