Under cared for Bearded Dragon

Question
Hello, my brothers bearded dragon is about 9 months old, he is roughly 14 inches long. Recently he has become aggressive, when i say aggressive i mean that we are able to take him out of his tank for a run around but as soon as we go to put him back in his beard goes a black colour and puffs out and he does not allow us to handle him easily anymore. My brother for the last 6 weeks or so had not been taking him out for regular interaction and play time, could this be the reason he has become so aggressive? I have decided to take on the role of being "Nando's" parent and need some help to get him back on track. If I keep handling him will he become friendly once again?

Another issue is that his legs are twitching, I read somewhere this is due to lack of calcium, I dont think the UVB in the tank is very good? What wattage should the bulb be at? Also his tank is at about 75 degrees during the day is this warm enough? Also rather then a tube cant u get a lamp?

Recently he has stopped eating much, my brother had been feeding him locusts, silent crickets and some wax worms and he was eating quite well. He also included some veg, such as lettuce, cabbage, brocolli and sometimes fruit such as strawberries ad blue berries. But as of late he has not been eating anymore?

He has recently only had a white light in the tank, could this be affecting the BD's mood? Before we used to have a red light for night time and he seemed alot happier?

His tank is taller then it is wide but can be placed on his side. it is about 18 inches x 10 inches and about 30 inches high?  

Answer
OK, sounds like you know what the problems are so get to fixin'.  The tank is too small, the temp is way to low.  110F in the baskng spot is what you are going for.  The UVB can e done any way you want but you must do it, and remember the coating on the bulbs only lasts so long.  Fix the problems, continue to hold him and things should improve.