Can I download my own models for free?

You can it easly

yes, you can setthe price to zero and then save. Immediately download your model and then reset the price as you want and save.

there really should be a feature to download own models, so you could tweak them if needed and reupload :(

There is a very small chance that someone could also download your model in that short timespan where you price the model at zero and then return it to your regular price.

You have to set the price 0 and download yourself.