Crikey you have some serious corrosion issues there.

I would be replacing that heater return pipe (after you get it off.).
Looks like you will need a new fan clutch and fan also. Unless you can get that last bolt out.

Picture no 2. that's the notch your home made tool gos in. You turn the fan around until you feel the tool jam into a hole in the " pulley holder". When it'
s in you shouldn't be able to turn the fan I would be using a bit of loctite or rust free on those bolts before you try to undo them.

The tool should be made from1/4 inch or 6mm rod.

My Engine compartment is clean because my car has been imported from Japan. When a use car is imported to Australia more often than not the underbody and engine compartment are steam cleaned. I have kept it clean since I owned it.