Gee, a one sided relationship. Sounds like fun? (sarcasm!). Do you really want to pilfer time from more worthwhile people and endeavors for this sanctimonious douche nozzle??? I wouldn't. FTS! Yes I voted 2.
I've had a lifetime of maroons I've spent waaaay too much time giving a bleep about only to have nothing but angst to show for it. NO. Life...is.....too.....damned.....short.

I'm wildly curious as to what he considers "magic words". The "magic words" I've seen lately in use are Obama, Hillary, MAGA, etc. that all magically absolve Trump of anything he has done or may do. Are these the magic words you speak of?

I would tell him that you are an adult and you do not want to engage in conversation where you "have to be on your best behavior." If he can't handle you expressing your beliefs when he is so vocal about his, that's his problem.

Why did he reach out to you? Where are his so called Christian friends? He has not contacted you in 10 years. Does he know you are not one of the flock? If he wants to renew an old friendship with you that's great as long as he respects your views and your personality or character. If you curse..you curse it's surly not a deal breaker..do it for humanitarian reasons but on equal terms.

I think you have a third choice which is to be tolerant by explaining that your unbelief would just upset him so it's perhaps best if you don't talk. Wish him well and move on. If he insists he doesn't mind then explain that he's not allowed to proselytize you and you don't want to talk about religion, you are interested in a respectful dialog on other topics.

It may be that he has nothing to talk about but religion, or it may not. Let him decide.

Do NOT get involved! Tell the guy that you feel for him an hope that he recovers, but that you are now too far apart in beliefs to resume the contact. If you resume the relationship, you will regret it.

I would say as kindly as possible that complying with his list of behavioral requirements would violate your own principles and that you must regretfully decline to continue conversation. He just might surprise you, though I'd be surprised if he was willing to negotiate on this. You're not really close friends since you haven't been in contact for a decade. It's not your fault he doesn't have people -- I would guess it's his list. So at the rist of seeming cold, if you have to choose between him and you -- choose yourself

Make it clear that you would like to converse with him but if it can't be done without the "god" bit, then you will not continue.

kick him to the curb

I would never be willing to censor myself in order to be friends with somebody. If he truly wants to reconnect with you, he should be willing to take you as you are.

Can't can't can't can't and some more can't ?
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Yeah, sorry, I cant.

But not at the expense of your own peace of mind.