Idiomatic Language – Proper Responses to ‘What’s Up’

It is a "display of confidence", meaning "submit myself to something unpleasant if I prove to be wrong" as in:

If the train arrives on time, I'll eat my hat.

To say "afterwards I had to eat my hat" is to admit that you were wrong.

http://www.phrases.org.uk/meanings/eat-my-hat.html

When you use an auxiliary verb for a third person, the main verb loses its 's.'

He walks toward a church
He does walk toward a church.

However, this change doesn't happen in first person; because, there is no 's' in the verb.

I walk toward a church
I do walk toward a church.

Especially when you are forming a question, the auxiliary verb is mandatory.

He walks toward a church? ~ Not a preferred structure as a question.
Does he walk toward a church? ~ Preferred structure

Why? Well, the questions are formed that way only.

It doesn't seem safe

You don't put 'seems' there because, as I said, when you put an auxiliary 'does' there, you remove 's' from the verb. Remember that way - the main verb's 's' is eaten by the auxiliary verb. But remember, this is not always a case.