answer:“If I were believing” won’t work. “If I believed in God, I would be called a theist.” (No “as” in any the answers.) “If I were to believe in God, I would be called a theist” also is correct and the same as my first example. “If I had to believe in God, I would be called a theist” implies that someone or something might be insisting, but this is also subtle. “If I answer your question correctly, what…” “Correct” is an adverb here and modifies the verb “answer.” “If I am correct, I have answered your question.” “Correct” is an adjective here and modifies “I.” You have a great day too (omit “ahead.”)