>"...you can set it so each damage dealt to the structure deducts some scrap."

Please elaborate on this. If I set it to 1, will it deduct 1 scrap per 1 point of damage? Or 1 scrap per single attempt? 

If you set it to 1, it will deduct 1 scrap per damage. So, if you hit it with a rocket for example, which deals 350 damage, it would deduct 350 scrap.

Is it possible to set it to a decimal? For example, 0.1? Or 0.01?

Yes! Absolutely, infact I would highly recommend doing that as it will provide a much more reasonable rate. I personally think around 0.1 is a good baseline if you want to go off that.

Thank you for the prompt response and the guidance!