1 - please do not try to make your own cable without a volt meter to verify your work.
2 - please do not cut the cables out of your power supply.  The power supply has a much longer useful life than any mining hardware you buy today.
3 - please do not try to make your own cables without a volt meter to verify your work.
4 - see #3

You are not going to get 7 R-Box connected via molex adapters.  They have PCI-E to barrel adapters for sale but they generally won't work on R-Box.

A 20 dollar break out board is probably your best choice at this time, but please, pretty please, find your volt meter before you plug anything into a miner.