When I go to custom world and change down the scale it starts to create the world but never stops.

1. Press customize
2. Change transform to below 100000.0
3. Create world

It should have just loaded up the world after a little bit.

I'm using the latest version.

This is because the current versions do not change the resolution of the data they request depending on the scale.
It has been addressed by @DaMatrix in #29. Until that's ready you should avoid generating worlds at small scales, that puts unnecessary stress on the web services because the mod tries to download a lot of data.