As far as adding a foam controller, I've never used them.
I would think your biggest problem at this point is finding a way to contain the mess.
If your airlock isn't clogged, I would say, let it work itself out. If it is clogged, then you run the risk of it really blowing it's top and having to contend with the aftermath. Maybe find a way to let the fermentation happen. Assuming you're using a bucket, put it in the sink and loosen a side of the lid?
I usually add a few drops of fermcap to my fermenter, just in cast. But I always add it when I transfer and pitch my yeast, not after it's going crazy. Can't see it hurting it though. Take off the airlock, send a couple drops down the bunghole (giggity) and then put your washed and refilled airlock back on.
Of course, a blowoff tube is an even better idea, but go ahead and give the fermcap a try.