Awesome mod, saves me the trouble of having spreadsheets on my other screen!

Is it possible to run Helmod outside the game though? I like a slower, more deliberate pace of play, so I often pause the game to do planning outside it. Would that be possible to do with Helmod somehow? To run it outside the game?

Short answer: No, that's not possible. Helmod is a mod for Factorio.

I'd recommend checking out YAFC (Yet Another Factorio Calculator). It's a stand alone program with similar functionality to Helmod. You can point it to your mods directory so it loads with exactly your set of recipes and settings.

https://github.com/ShadowTheAge/yafc

Helmod does have an «automatically freeze the world while its main panel is open» button on the top right.