Second ticket is an award ticket
I don't think AY will care much if you miss your HEL-OSL. If you have checked-in baggage, you may have some struggle negotiating the short checking and while AY is usually pretty lenient there you never know for 100%.
The one thing I would do is not to have the same ff number on the two tickets.
Well so far both tickets have the AAdvantage number on them. But the HEL DFW is an award so no miles. I'm not even sure how not have the ff number on the ticket??