The spray head being clogged wouldn't cause it to leak. It has a little rubber disc in it that deteriorates over time. It's probably going to be easier to just replace the whole thing, as I doubt you'll be able to find just parts. Most hardware stores should have a new one. If you want to by-pass it, just cut it out, get some shark bite fittings (or crimp fittings, if you have the crimper), bend the tubing around & tie it together.
The actual purpose of the vacuum breaker, in the first place, is to prevent sucking sewer/drain water into the fresh water supply. I am assuming this line is going to the black tank flush "sprayer".
The fresh water supply could possibly get contaminated if you were cleaning the black tank via the hose connection and the water got shut off or a fire hydrant the street was opened. This would cause a suction on the garden hose/hydrant, thereby sucking the water from the black tank. That's the purpose of the vacuum breaker, to cause a break in the vacuum/siphon.
Bypass it till you can get a new one would probably be ok, but I think I'd like to replace it as soon as possible. Especially being where I think it is.