Definitely has MBD...there are so many things you are not doing right. BTW he has more than one bad arm break.
Asap...like yesterday... he needs to see a vet and start on liquid calcium such as liquid calcium sandoz or gluconate. You need a vet to tell you how much and how often to give it to the chameleon.
Once his bones and muscles, etc are healthy again you need a proper diet for him and the insects and a proper supplement schedule. You also need to gutload the insects. I'll cover that further down.
He needs a proper UVB light. I would get a LONG LINEAR Reptisun 5.0 and put it on the roof of the cage which I hope is screen (not glass or plastic) .The hood for the light you use should not have glass or plastic covering it either. If it's warm enough...80F or so...then get the chameleon outside in the sun but make sure you don't leave it out long enough to burn because in the state its in it might not be able to move out of the sun when it's had enough.Sunlight and the UVB light will allow the chameleon to produce vitamin D3 which will allow it to use the calcium you're going to be giving it to build it's bones back up. MBD also affects the muscles and other things...so you may find the chameleon is constipated or it's digestion is slow.
You need to be sure the temperature range in the basking area is in the mid to high 80's F so the chameleon can digest it's food properly so you need a thermometer. You need a white light producing regular household incandescent bulb in a hood for a basking light....this should sit on the lid of the cage or hang just above it too.
You need to get rid of the fountain and the small pebbles in the cage. The fountain is a breeding ground for bacteria.
The pebbles could be ingested accidentally and kill your chameleon. You can put rocks in there that are way too big to fit in his mouth ever if you want to.
Now for your husbandry...replies in red....
How are you gut-loading your feeders? I feed them the flickers jelly stuff that’s about it. Ditch the jelly stuff and use dandelion greens, kale, collards, endive, escarole, squash, zucchini, sweet potato, sweet red pepper, carrots, etc and a very small amount of berries, melon, pears, mango, papaya, or apple, etc. To gutload superworms, crickets, roaches, locusts, etc. Hornworms and BSFL and silkworms are all good foods for the chameleon too.
Supplements - What brand and type of calcium and vitamin products are you dusting your feeders with and what is the schedule? Repti calcium, I do this about once a month or less /:. It's recommended that you dust the insects with a phosphorus-free calcium powder at almost every feeding to help make up for the poor ratio of calcium to phosphorus found in most feeder insects. It's recommended that you dust twice a month with a phosphorus-free calcium/D3 powder to ensure that the chameleon gets some D3 without overdosing it and leaving it to produce the rest of the D3 from it's exposure to the UVB light. D3 from supplements can build up in the system and lead to health issues but D3 produced by exposure to the UVB light won't as long as the chameleon can move in and out of the UVB at will. It's also recommended that you dust twice a month with a vitamin powder that contains a beta carotene prOformed source of vitamin A. PrOformed sources of vitamin A won't build up in the system but prEformed sources can. However this leaves it up to you to decide if/when your chameleon needs prEformed vitamin A. This schedule can be started now too.
Watering - What kind of watering technique do you use? How often and how long to you mist? Do you see your chameleon drinking? I have a fountain where he drinks water I usually see him drink water, I don’t mist his cage because I have a little sister that usually grabs it and idk what stuff she puts in the spray bottles no matter how many times I buy a new one she takes it You need to solve the problem with the mister. The cage needs to be misted long enough at each session so the chameleon will be stimulated to drink. You should also have a dripper running. It can be a deli cup with a tiny hole in the bottom so it drips at the rate if one or two drips a second. This should run long enough to make him drink too.
Fecal Description - Briefly note colors and consistency from recent droppings. Has this chameleon ever been tested for parasites? Has not been tested for parasites. The last dropping I saw was white and yellowish, little bit of clear liquid Yellow in the white urate part (pee) indicates dehydration . There should be a poop/brown part to the droppings too....but it won't be there if he's not eating.
Lighting - He has the light on from 8-9am until 8-9pm He should have a UVB light and a basking light as I described earlier. No lights on at night
Temperature - you need to know the temperatures and they need to be right...mid 80's F basking and low to high 70's F in other areas of the cage.
Humidity - What are your humidity levels? You should measure this too.
Plants - Are you using live plants? If so, what kind? I have a bamboo in his fountain. Ditch the fountain...mist and add a dripper and run them both long enough to stimulate drinking.
Placement - The cage is on my room floor I would raise it up several feet off the floor.
Location - Where are you geographically located? I live in California if this is what it’s asking
As you can see there is a lot to do to help this chameleon before it's too late....and it will be too late very soon if you don't start yesterday!
Good luck.