Welcome to being owned by a beardie! It's an amazing experience. Toothless looks like a healthy fellow and we'll be happy to help you keep him that way. Purchasing an older dragon is always a selfless thing to do. Everyone wants babies, and often the older ones get left behind. He's still young enough to bond well with you and give you years of love.
His flooring is actually one of the safest and most sanitary out there. Sand tends to hold bacteria, so short of dumping it all out and sanitizing the enclosure every time they poop, it's not a very clean substrate and can actually cause health problems from the bacteria, dust, as well as impaction with some sands.
Feed him all the appropriate sized insects he wants in 15 minutes once each day. Superworms, crickets, roaches, silkworms, and phoenix worms are all healthy choices for him. He should also be offered a salad every day. Choose from items in green on this chart
for healthy choices. Items in black can be added in small amounts once or twice a week as a treat.
You don't need to actually bathe your dragon unless he walks in poop or gets yucky in some other way. If that happens use baby shampoo and a very soft bristled toothbrush to clean him. Otherwise, let him soak in lukewarm water 3 or 4 times a week for 15 minutes or so. That will help keep him hydrated.
You can clip his nails if you need to. Just take the very end of the tip with a regular set of nail clippers. I keep a rough rock in each enclosure for them to climb on. It helps keep their nails trim naturally.
Do you know how old his UVB light is? What brand and bulb style (compact/coil, tube, etc) is it? The brand and rating should be stamped directly on the bulb.