You only need to spot clean pee daily or every couple of days, don't be in too much of a hurry to clean up poo when you see it as they need to eat some of that, it's how they get all the nutrients out of their food.
It depends on the size of your cage really but I would say about a third certainly no more than a half of the cage every three to four weeks is plenty with cleaning.
Does he have a sand bath with chinchilla sand (not dust)? It's important for them to have one & they will often pee in the sand which can make cleaning even easier!
Dwarf hamsters are even more at risk of injury from bumping into things or getting their feet trapped in the air holes than syrian hamsters due to their small size, it's really not worth the risk & they don't offer a hamster any kind of enrichment really, if they just want to run they can do that in their wheels.
Playpens serve two purposes really, one it gives you ham new things to explore & two it gives you a great opportunity to interact with him.
There are some examples of playpen set ups you might find useful here.
Let's see your playpens!
It's best to begin with short sessions of maybe 10 minutes in the playpen, see how it goes & as long as your ham appears to be happy you can extend it to as long as they like.