Is Zakat obligatory on an additional house that is not inhabited by its owner, and what is the value of this Zakat? Also, is it permissible to say, "Allah has provided for me and more," or "Allah has given me more than I deserve"?

The statement "May Allah grant me more than I deserve" is not permissible, because a servant has no right over Allah, and provision (rizq) from Him is a grace and a favor. As for a house that you do not inhabit, there is no zakat on it, unless you bought it with the intention of trade, in which case its zakat is obligatory by appraising it every year.