As you know or have figured out, the RF environment up a radio/TV broadcast tower can be a difficult challenge... We have several clusters of APs and three backhauls on an FM tower, and have been successful after careful efforts.
As others say, good shielded cable and solid connections are a must as a starting point. Ensure your surge protectors are reliable, well grounded, etc. And try ferrite chokes at the ends of your ethernet runs. http://community.cambiumnetworks.com/t5/PMP-450/PMP-450-hell-on-FM-tower/m-p/36502 is a thread on essentially the same subject, though the OP was talking about PMP450 gear.
We just recently revamped that tower, actually, putting a custom-built 2'x2'x4' aluminum enclosure in place about 300ft up the tower, containing a 19" rackmount router, various POE injectors and backhaul IDUs - so far we're maintaining gigabit ethernet everywhere we expect it. (backhauls and CMM4 etherWAN switch, the three ePMP APs up there are NOT currently gigabit-capable, deriving POE and sync from the CMM4)
Disclaimer: I'm the networking guy, not the RF guy.
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