First, the constant mullah word is a bit annoying, why not say Imam? Khair.
1: You can have a strong faith according to yourself and yet not follow every command of His swt, at the end of the day, it’s something between the Creator and His slave. The rest of us can only guide and advice.
2: The bold part: It’s possible because some people don’t mind “converting” on paper - so the Imam is usually told that the guy has converted and hence he will willingly perform the Nikah because for some people it isn’t a big deal to shop within religions.
3: I have never heard about any nikah between same sex, and quite frankly I don’t even know why they would do it anyway, I’m sure they are aware about what Islam says about homosexuality
4: Muslim men are allowed to marry women who are Christian or Jews. This doesn’t apply to muslim women.