wp-scripts start build hangs

Nothing is hanging. It’s just waiting for a change so that it can automatically build again. That’s what start does. If you just want to run a build once use build.

The warnings in your second example are self explanatory: You’re using a font asset that is very large and exceeds the recommended maximum size. The second warning is just a summary, and is repeating the same information. Looking at the font in question I can see why it’s so large, so you’ll just need to decide whether you want to make that trade-off.