Those seats are crap to be honest, as is the valve in one piccie.
It might pay you anyway to re-anneal the headgasket first, but this isn't the problem, just might as well while it is off.
If you have pressure going in and then coming out through the port the only connection point is past the valve.
The dull shiny bits tell you the valve HEAD is bent, so new valve needed, not expensive on a series, and bloody good engines as well, what head is it 12G940, 12G295 etc
tabetha