Should one leave a suitor who curses religion and claims he did not mean it, and is accustomed to doing so, or is it permissible to marry him if he does not change?

Cursing the religion is apostasy by consensus. It is not permissible to marry someone who curses the religion unless they repent sincerely. It is not sufficient for them to say that they did not mean it or that they are accustomed to it. One must verify the soundness of their state after repentance. They should also be advised about the gravity of their action, and one should be keen to marry someone of good religious practice and character.