not exactly. It should be: 'Til death do us part 'Til is an abbreviation for until. Till is something the cashier puts your money into at a supermarket.

In older forms of English, most conjunctions took the subjunctive; e.g. "before I be put to death", "If it be the last thing I shall ever do"... It shouldn't be 'does' because in 'Til death do us part' we are using a subjunctive. I think you should look at this phrase as an idiom more than anything else.

Yes

It's also sometimes "till death us do part." Either way, yes, grammatically correct, and even if it weren't - that's the phrase.

Definitely. It is probably considered archaic nowadays, but still correct.