Are you sure about the calcul ? From many billions to 47.5 years... its maybe a little bit optimist.

Special relativity is what it is. I am 100% sure (and this can be easily verified by anyone as I give all details). What is not said is that this implies to reach a speed equal to the speed of light up to many many digits. That's the trick behind.

Are you taking in consideration that the universe is in a contant expansion ?

I said there was an imprecision on the reasoning. You found it. I should have said: the limits of the universe today.