So the OP's primary concern is the COS issue?
Based on all the other things written, I wasn't sure how many issues she had.
COS are not allowed in the exit row, period. There are regulatons regarding that. If anyone needs a seat belt extender, they are not supposed to be in the exit row, at least that is what I have read and found out the hard way.
I had a similar experience in an exit row (the COS sneaked in her own seat belt extension so she could be buckled in), and I will not make the mistake of sitting silently if this occurs again.