It is very easy to put holes on that rubbermaid. It doesn't even have to be round holes. If you don't have a screwdriver (get one! It's a buck at the dollar store and you can use it for all sort of stuff like replacing batteries and such) you can just go get a knife and punch an X into the sides of the bin and poke it from the inside out with your fingertip. I'm gonna flip if you say you don't have a knife...
Anyway, once you put a water bowl inside that rubber maid you can easily get humidity close to 100 with that UTH. You will notice a lot of condensation on the lid of that rubbermaid. Especially when your snake spills his water bowl onto your substrate.
Sure you can do air exchanges if you open the tub daily to handle the snake. But, when your snake is in shed, when you want to go on a weekend party, when you get too busy, you'll find out soon enough it will not always work out that way.