Yes, a PTA is always possible and if the intercont flights are booked on SK-metal it is a nice profit for SK and they should offer a PTA in this case, but not if there were only Delta-flights.

I also think it could be solved at the gate, when I was at the gate or check-in and there was for example some disabled person or someone with a broken leg I simply moved someone and gave them a good seat. Also a sales agent can always send a request to the seating department in DK and ask them to fix seats if the agent-error is explained to them.

I hope everything will be fine for you, if I was still at SAS I would have arranged it for you