Bathtub taming is easier than a plastic box
Your 10 year old could get in the bath as well (first probably). I used to let our hamster walk into a hamster ball (or into a tube and then from the tube into the hamster ball). Pop the lid on and use the ball to carry him to the bathtub, where you can set the ball down and take the lid off - after your 10 year old has got in the bath. Although might be best to do a couple of sessions without your 10 year old in the bath first - so you all get a bit more confident.
He'll probably just slither up and down the side of the bathtub trying to get out at first, but while he's doing this, you can gently stroke him on the back with one finger. Just two or three strokes then stop. If he jerks his head round then wait and try again later. Next session do it again. Eventually he will stop jerking round and that is a milestone - he has accepted the touch without being scared.
From there you can move onto cupping a hand under him as he walks around in the bathtub (put a couple of tubes in - kitchen roll inner tubes are fine although if he's a bit big for those you can slit them down one side so they expand). So the back of your hand flat on the base of the bath, palm up in front of him and let him walk over your hand. Do that the odd time. Next session when he walks over your hand, lift your hand slightly - just 1cm or two - but let him walk off. Then do the same but lift a bit higher. By then any of you should be able to handle him and he'll be tame. Even then they can occasionally get a fright from a noise etc and can "ping" (wriggle free and leap two feet in the air out of your hand) so always best to handle them over something soft and low down - eg over a cushion or sofa or bed - when he's tame enough he doesn't do a complete runner.
It varies how long it can take - it might be one or two sessions - it might be 7 or 8. But when you get there it's worth it. It sounds like he has accepted touch already.
With our first syrian, who was from a pet shop, it took us about 2 months! Bathtub taming every 2 or 3 nights is better than every night - give them a night or two off in between!
As they others say, when they are babies they can get exhausted. Same if they run in their wheel too long they can flop. I would leave him for another night.
Don't clean anything or move things around in the cage or change anything for the first two weeks - they need that time to fully settle, claim it as their own and scent mark everything (this actually helps them find their way around as they don't see well).
Unless something is dangerous and needs replacing of course.
I only do a cleanout about every 2 or 3 months! But that is with 5 to 6" of substrate/litter and a litter tray. They are quite clean really and choose a spot to pee - you can just spot clean that a couple of times a week and leave the rest of the cage a lot longer. When you find out where his toilet area is, it's a good idea to put a litter tray there, with Chinchilla bathing sand in it. Put a tiny bit of smelly pee substrate on top the first time so he knows it's still his toilet corner/area. He should use it - then it's easy peasy - you just empty the litter tray every few days and replace the sand. Don't worry about poops - unless they start taking over in a big way, then spot clean them. Their poops aren't dirty or smelly and sometimes they eat them or hoard them - which is normal! They have two stomachs and can redigest vitamins etc from their poops - poops are emergency food supplies. You can cull them when you eventually clean the cage.
Even then it's best not to clean everything at the same time as that removes all of their familiar scent and they feel very stressed and lost. So when you change the substrate just do that - and keep back some of the old that is clean and spread it on top so it still smells familiar (that top layer will gradually get spot cleaned out). Then do the wheel another week, any other items that need cleaning another week again.
I always leave the nest alone - unless it's pee'd in. They are particularly fussy about their nest and hoard. I also leave the hoard - unless it's pee'd on. If you do need to remove the hoard always replace it with new food in exactly the same place and it's best to try and leave some of the old familiar smelling hoard behind if there is some unsoiled. The dried food is fine left hoarded for some time. It can be pruned when you change the substrate if the hoard gets very large.
Same with the nest. If it's pee'd on then you'll need to remove it but try and leave a little bit of the old nest behind - even if it's a bit whiffy. Then put a big pile of new nesting material (torn up strips of plain white toilet paper are best) somewhere in the cage - but not actually in the house - they like to forage for it/pouch it. If the nest isn't pee'd in I just leave it - they tend to refurbish it themselves and can build really big cosy nests.
The business with the hoard is quite important as it can cause anti trust behaviours if you are seen as the thief! They get really quite anxious about guarding it and won't come out - or even start peeing on it to deter thieves - which can be a bit of a vicious circle but don't worry about that yet!
I should just leave him quietly tonight. Does he have a wheel? If so, put a bit of substrate on top of it before you go to bed and see if it's gone in the morning - if so he's been up and using his wheel in the night.