also, I think there should have been a two-sided arrow in the reaction, not a one-sided.
Potential difference is not large, but the direction of the reaction is quite obvious.
No idea how you got 0.0029 V, it is an order of magnitude too low.
It is a trivial question, my bet is you have overcomplicated it.
(BTW: -0.403 V, not -403 V)