Is it the Repti-Sun 10.0 fluorescent tube that you got at Petsmart? If it is, then you don't need any other UVB at all as this bulb is a very good one. It should be placed 6 to 8" from your beardie while in the basking spot. How often are you dusting with calcium and vitamins?
As far as the reptile sand goes, it would be a good idea to remove it from the tank as that may very well be what's causing the impaction problems.
Since he's not eating, would be best to pick up some chicken and squash baby food, dilute with a little water and put drops on his nose for him to lick off. Please be sure to keep us updated on him.