I use just warm water not hot water and never had an issue on my personal vehicles. De-icer spray is a good idea but some are corrosive to metal parts.
The car heater/defroster has been the culprit in most cases of windshields I've replaced for customers in the winter time but that's because they had rock chips that they neglected to have repaired. I don't recommend Ice scrapers simply because they Do scratch. Yes plastic scratches. In very cold climates I guess you have to use Ice scrapers but most areas of the U.S. warming up your car before driving suffices. It is a good idea to warm up your car anyway before driving especially at 10 below Just my opinion.