Tips for My Newly Adopted Beardie Please :)

Hello, this is my first day and first post on being here. Im new to owning a bearded dragon and i probably wouldnt of ever gotten one till my dad bought a tank and equipment at a garage sale and said i could have one. So i did hours and hours of research bout baby dragons and Bearded Dragons in general and then i was asked at my school a question. I currently work in an aquaculture(fish) room taking care of them over the summer and Spike, the Bearded Dragon has been in there so i can care for him and its a heated room in general.
I dont know his age, how long hes been there but i know this. he has been fed dried mealworms and pellets yet ive never seen him eat them. To be honest I dont know how he is alive. for his size he seems skinny and I dont know the last time hes truely been fed. SO being asked if i wanted him after thinking about it i couldnt deny it. why buy one when you can save and adopt one? well so i talked to the asistant principal who helps me out alot and with some school money for the aqua room she bought him calcium powder, and 2 containers of about 36 crickets. it took maybe 2 or 3 days for him to eat all the crickets in 1 container but im sure f he was at my house i could of fed him more. im about to go on vacation and my dad refuses to take care of him at the moment. so i got him some fresh basil and tomato and peeled the tomato alittle and broke everything up and ive been spraying him and giving him calcium dunked crickets but one thing i want to know is ther a way to estimate his age? also hes been stuck in a super small cage which would of been small even for a baby so i transfered him to the biggest cage at the school and when i get back on the 9th or july im hopefully going to buy a 55 gallon cage from the guy.

One thing for mesuring is that he doesnt have his full tail. i dont know how or when but at one time it must of broke from some jerk of a kid or soemthing but its extends and then turns into a nub. i will post pictures when i get back. Another question is what should be the proper weight of him? he seems to be about 1ft maybe alittle more.

I bought him a harness and attempted to put it on him but since hes not used to being handled today was the first day ive actually been able to pick him out of his cage and he be semi-calm and still at points.
I dont know the exact temps in his cage on the warm and cool side but i do have the reptile light and then i have his heat lamp. i have a small thing for him to climb and i also have a little hut for him to go in and climb on. it has reptile carpeting for the bottom and he also has a dish that i add water/veggies in for him.

if there are any tips that anyone can give me or help me answer my questions it be much appreciated. i am just a newbie to bearded dragons, i know some of the basics, but if told the hidden secrets i can hopefully give spike a better home at the school and then at my house when everything is all set.
Thank you

Hi welcome to the site! Bearded Dragons are such great reptiles to keep, I love their great personalities. Ask any questions that you may have, When you get a chance you can read the sites caresheet on bearded dragon in the caresheet there is a link to their diet.
A lot depends on the age of the dragon. Hatchlings (up to 5 months of age) require mostly protein 80% protein to 20% greens, because they are growing that they do in the first months.
Juveniles (5-18 months of age require 50% protein to 50% greens. And adults (18 months and older) require 20% protein to 80% greens. So their requirements change as they age. Temperatures are also very important for proper digestion of their food. one side of the enclosure should be the hot side and the opposite side should be the cool side. You should provide a hide on each side, water should always be available even though they will get the majority of their water from their food. They should have a basking spot of a temperature of 105-110 degrees on the hot side, ambient temperatures of 85-95 degrees, and cool side between 75-85 degrees, nigh time temperature can go down to 75 degrees. The best way to measure the temperatures is with a digital thermometer with a probe, the probe can be placed anywhere you want to know the temp, it's always a good idea to know the basking temperature so by placing the probe of the thermometer directly on the basking spot will ensure that you know those temperatures you'll want them to be between 100-110 degrees. UVB is also very important, it provides vitamin D and is needed for the absorption of calcium.

Here is the sites caresheet, great information to always have at hand.
Bearded Dragon Caresheet (Pogona vitticeps)
And here is the diet, remember that the staples are the most important part of the green part of the diet. I would print this off and keep it close at hand.
Feeding Bearded Dragons (Pogona vitticeps)
Any other questions don't hesitate to ask.