You cleaned up the outside of that yoke really nicely,
... but ...
I wouldn;t even think of using it as it sits.
The inside of the yoke has to be able to slide easily on those internal splines as the motor/trans moves around under load.
Any binding there will cause all kinds of issues/noises/harmonics/unecessary wear, and anything that is scraped/sloughed off will contaminate the .6 of a quart of lubricating oil that keeps the t-case alive.
The good news is that it's not really that hard to cleean the internally splined portion.
It's too far gone for just a bottle brush (found in the baby section at most drug stores) They are usually enough to clean light deposits and other junk out of the internal splines.
However, a metal gun brush and some wd-40 will probably clean that up just fine.
Just go to your local gun store and pick up one that's in the same diameter range as the major diameter of the splines. (If the store owner asks, tell him you've got a home built single shot cannon /ubbthreads/images/graemlins/devil.gif )
Just spray things down inside with wd-40 and plunge the brush straight in and out, don;t try and rotate it inside, it'll distort the brush strands and you need them facing straight out to get down into stuff that's at the base of the splines.
Wear safety glasses and blow out the contaminates with compressed air, and follow up with brake clean or other evaporating solvent.
Doesn;t have to be "perfect", but rolling the dice on a t-case failure is not a good bet.
It's also worth noting a new yoke is ~$30 from the dealer, and some time to install it.
Another option is a small metal toothbrush from harbour freight with cut down bristles