Really?? But then a $1200 BFOD is hardly likely to include 5 stopovers, lay-flat beds, lounge access etc the OP would experience flying J. A better comparison would have been the 280k points + roughly $1500 such a J award would cost.
The OP's post is weighing up two options: (a) buy a regular BFOD economy fare and possibly maintain silver or (b) splash out and use accumulated points on a OneWorld Classic award and not maintain silver.
Your third option ((c) spend $6-7K on a business class RTW fare) is an order of magnitude different from (a) and (b) in terms of cash outlay.
OP, definitely go with (b). You won't regret it.