Glad you're enjoying the game so far!
There is a bit of improvement possible still but the game might only go down to 1.5GB due to general size of videos, audio etc.
I can try to add a more compressed version next to the current one, where videos are not running in 60fps and images are compressed further (but will have visual loss).
For the future: Episode 3 for example will be its own .apk
Same counts for every other future episode. That means you only have to download one, ~1GB episode at a time and can delete the old one so the files won't get to big.