does sound like you might have a bad radiator,as far
as the crumbly fins,are you sure that is the front of the
radiator and not the A/C condenser? in any case i have
never seen that problem but some road chemicals might
attack the aluminum.Have seen cracks in the plastic
radiator tanks leaking coolant(the tanks are replacable-
replaced a cracked tank on a'95 olds aurora once,got
new tank at dealer,repair wasn't too hard

)
If your fan is not operating you will find lots of posts
covering that problem