I don’t think the hoard sounds too large
. It makes them feel secure and they are very precious about their hoards. They tend to forage and pouch from the food bowl and scatter feed and only actually eat from the hoard. I bet he loves that house. They can put “special “ things in a different place as well. Our hamster sees half a walnut as a special thing so puts it in his toilet/litter tray of all places! (Theory is that deters anyone from stealing it if it’s peed on but just makes the walnut go black and manky. If I see it I take it out and put it next to the potty instead- a few times - then he gets on the habit of leaving it next to the potty.
As regards the amount of food, I just put the same amount out. A desserstpoon full. If quite a bit left in the bowl I do it every other day. If your hamster is clearing his bowl daily and hoarding it all then yes it will mean going through quite a bit of food, a lot of which will get wasted. But it’s a balance. They need to forage daily to have normal behaviours. If less food appears they could actually get anxious and hoard more than usual.
Not sure how much you put in his food bowl but I tend to put a dessert spoonful, of some still there I miss a day but then scatter a few pumpkin seeds as a treat for foraging. On the third day I throw away anything left in the bowl and put a new spoonful out. Only because they seem to ignore good that isn’t freshly put out and only pouch the newly put out stuff.
They hoard more than they eat because they are hard wired to hoard supplies in case of food shortage. I’ve found one hamster would actually put sand in his hoard as well - maybe to preserve it? And you may find a pile of hoarded poops as well - they can eat poops for emergency food supplies - they have two stomachs and can redigest nutrients from poops - a survival mechanism. So if they eat one it’s quite normal
What I tend to do - with regard to size of hoard - is leave it till a substrate change - which I only do about every 2 to 3 months as our hamster uses a litter tray for peeing so empty that every few days and the occasional spot clean of substrate etc if necessary during that time- gives minimal disturbance. That is with a good substrate depth of about 5”.
At that time I “prune” the hoard and take out most of the bottom section - which is old food and can start to deteriorate (they do tend to only hoard dry food and eat fresh food straight away so if you only give a tiny bit of veg daily no need to worry about that). I leave the newest top bit of hoard where it is - or put it back in the same place. They often have their main hoard under their nest. If there is enough substrate under the nest to do that.
However if the hoard is starting to fill up the house to the point he can’t get through the door then maybe (when he’s not looking!) remove some from the bottom but leave the top newer bit in tact. If ever you have to remove any though give a special treat or scatter a few treats in the cage to make up for it or distract them from their hoard being messed with!
Sometimes you do need to remove a hoard of it gets peed on as that is unhygienic and can go mouldy as well. In that case try and leave a little bit behind that is dry and add some new food in the same place so he still has a hoard - ie replace some of it.
Hoarding behaviour can lead to some issues as if they fear it being “stolen” then they can pee on it to deter people stealing it - then you have to remove it so they pee on the new hoard - it can be a vicious circle. You can break that though and if it becomes an issue I tend to put the new replaced hoard “near” the old one rather than in the same place to stop the pee cycle in that spot.
All hamsters are different and have different personalities. Yours sounds a bit like our last one, Newt, who I used to call my little hoover. He literally hoovered up all food.
They do need routine and can get fearful of there is no food available so they do need food providing each day even if they hoard most of it. At the end of the day I think hamster food is not that expensive and a bag lasts a long time and it keeps them happy.