Don't worry much about denied boarding - it's very rare (1/10,000 or so in the US, where they publish these figures).

Even as OW ruby you'll be ahead of others with no status at all, plus people can cancel on the day - and they often do as point-to-point tickets are flexible on the day of travel (though your award ticket will be completely inflexible. As has been said above, the fact you are connecting should also help.

I'm sure that if there were higher status cardholders fighting for seats in the cabin, they'd have booked the exit row by now - so I wouldn't give it a second thought until a week in advance.