I was looking at seatguru and it showed seats 12AB/FG as bad seats. How bad are they? 12CE are already taken, and it seems row 5 is blocked, even for elites. Are there any other good seats in Y?

They are bad indeed. the Dash props have more leg room in the emergency exit (1CDF). Best is the bulkhead 12C or E, since you can stick your feet out in the section ahead of you, while these seats actualy have an inch or 2-3 more legroom than 12AB or FG

With 6'7" I find this the worst exit row seats on any flight to Europe. Many local flights have more room in the exit rows.

However, bulk head is even harder to get, even for preferred flyers, so if you have to, take 12ab or fg. They are at least somewhat better than the standard coach seats

Is row 5 blocked until the day of the flight?

Is row 5 blocked until the day of the flight?

Not sure. If you are preferred they should show open or occupied.

I just flew BCN to PHL on 12G. Not much leg room and it was freezing. The emergency door does not seem to have the same insulations as the rest of the plane. 12 c, D and E had a lot more leg room.