I don't think there is a major problem with your monitor. Everything looks pretty healthy, and he looks to be in great condition.
I'm not exactly sure on the growth rate. You should notice when you have a full grown 6 ft adult weighing 75+ pounds though
You have to remember its instinct is to kill and eat so you can never ever trust a reptile! suposedly they are the tamest monitor. You can tame them to be a big puppy dogg.
Does anyone know anything about orchid bark? Is it harmful in anyway I am getting a 240 gallon and a guy that I know is going to give me a great price on 150 quertz. 30 dollers i bet you cant beat that j/k(lol) but for humidity i would mix peat moss with the orchid bark is that bad?