Is there something wrong with me?

It doesn't sound like there's anything inherently wrong with you for having this thought. People often have unique and introspective ideas, especially when it comes to complex relationships like friendships that originated from past romances.
Your suggestion of making a promise to attend each other's funeral if one of you dies first might be a way of acknowledging the significance of your past relationship and the current friendship, while also respecting the boundaries you've established by choosing not to be in regular contact.😊

Caring at the end I think is more important. Jealousy I'd be concerned about at a wedding

Maybe you are still feeling the void or have not replaced someone with that deep emotional and heart felt relation. Maybe there is some deep attachment that you still feel for him.

Just do your life and let him do his.
If you feel it's appropriate just go to his funeral when the time comes.

I think it would be a great thing if you drag your mind OUT of the pit. Do NOT suggest that to him...not unless you want him to wonder if you are losing it.

That is a rather odd request. He will probably say "umm... OK" or something, not being really committed. He may be more worried you are thinking of suicide.

No, I don't think so.

Cause you don't want him at your wedding? Or you are afraid to ask?

Are you depressed?