First; I know the wind is your friend.
2nd; It was really windy this morning on FORK, and I caught fish. Not like I thought I should and not many for the spots I fished and the fish I marked.

So,,, my questions are:
Is there some point that it gets "too" windy, even for the fish to be active ?
Do they hunker down behind structure to keep from being blown around too much & turn off to feeding ?

I don't have a full answer to your question. . .but on the smaller bodies of water I've fished, as long as the surface isn't frothing, the fish still bit. I've fished in wind that most would say isn't fishable and still caught like I would expect on a normal day. But again, these times were on really small lakes where the wave action isn't really too dangerous and there not really enough room for much current to develop.

I absolutely suck at fishing in the wind, I can barely keep control of my boat, let alone focus on feeling bites. Anything over 15 mph usually means im gonna have a rough day, I also have heard the wind is your friend, but it has not been the case with me yet.

I like the wind to a point. I have found that they bite better in a good stiff wind then have the bite slow down if the wind lays down. But if it's blowing hard enough that my TM comes out of the water it seems to spook them even in 20' water. IMHO

wind only blows above the water not below it but wind does create current but not to the extent to where 20mph winds create 20mph currents if so i would go on the windiest days and get downwind cause the bass would be stacked in by the k's