so, you are missing pins on 23DB connector? they are hard to find, people usually hack the 25pin.
3 wires is more than enough, you just need couple of right resistors, depending which voltage you choose. there are schematics on net.
forget YPbPr, it is not worth the hassle or money.
if you never soldered before or don't have a friend who does it, I'd just buy another cable, they should be cheap nowadays. ask seller for schematics or some guarantee.