To be honest, I think you’re over stressing.
He looks happy and that matting is great. I can see the UVB is the tube (which is correct) and you’ve got a heat light that is well placed etc. the only possible tank alterations I’d make (other than getting a bigger tank when you can afford it) is that beardies tend to enjoy their basking spot being a rock or a log (if you can’t get a rock at the right level). They like to have their tummies warmed up as well as their backs. If I’m not mistaken, cold tummies can lead to digestion problems.
He looks like he loves his matting but perhaps it could be moved or a flat rock put on part of it?
Otherwise it’s just the simple things you would have read - the insect-veg ratio depends on age. Gut load crickets etc. dust them with calcium (I add a multivitamin to my boys veggies to ensure all is well, if you do that, make sure the vit A & D are suitably).
If you have the door open, make sure it’s not creating cold areas. I have my boys lid up when it’s hot, but down when it’s cold - but I live in eastern Australia, so the natural humidity is different.
He will take a while to settle in and you’ll need to possibly make up for his previous owners mistakes (I rescued mine, so he was malnutritished, skinny & lethargic due to having no heat lamp at all for almost 2 years).
Where did your boy come from? He looks pretty healthy, no eye puffing or lip sagging. Their tongues do look pretty pale in general so I wouldn’t worry about it. But make sure his mouth isn’t goopy or sore. If he opens his mouth, check for red marks.
It’s ideal to take a fecal sample to a vet so they can ensure there aren’t any parasites etc.
Otherwise they are hardly little bastards who can handle most of what life throws at them. Often they want love and cuddles, though it will stress some out, so you can play that by ear.
Their fecal matter is forever changing consistency depending on what they’ve eaten. So long as it’s not too mushy & they don’t get constpation or impactions. You should be all good.
Stop stressing and just enjoy him. He’s checking out his new environment (possibly seeing his reflection in the glass and trying to work if it’s friend or foe).
Just give me lots of healthy foods and lots of love and you should be all good. You’ve done everything right that I can see