I say "Well bless you, too." LOL No, really! I make it sound as ridiculous as possible, however. (Which isn't difficult)

I don't bug about. Thank you is perfectly fine. It seems more polite and social than anything real anyway so... whichever.

How many languages could we say "thank you" in and should we humorously apply them? "Domo Arigato!"

Why do you feel a need to comment on one bodily function but not others? Why is sneezing special but coughing, etc is not?
The blessing is not a christian ritual but an ancient belief. It may be an odd at first to stop but it really isn't rude to not say anything.

Though I'm an atheist, I always say "bless you" to even the strangest of strangers when they sneeze in my proximity. It's a good way to connect with another human for at least a few seconds. Most people, from my experience, seem to appreciate the concern. In early, pre-science days, it was thought that sneezing was the releasing of evil demons.... thus the need for blessing. In truth, the explosive discharge can be fraught with evil demons, such as flu virus. I think a "thankyou" is an appropriate response...... thank you for thinking of me.

Egészségedre or Gesundheit. both phrases are steeped in old superstition.

I say, "Thank you." Seriously, I'm not that narrow.

I say thank you, when someone else sneezes I say Gesundheit.

Not sure, but I have stayed silent after Somebody else's sneezes

Sorry i just blew mucus in your face.

Sure, it has become a saying devoid of its religious meaning much like goodbye (God be with you). I do tend to say Gesundheit if someone sneezes near me though!