If you smell coolant with the heat on you may have a leaking heater control valve; if you greenish/whitish corrosion on the valve when viewed from the passenger compartment, you have a leak.

If your windshield is leaking you should pop it out, replace the rubber gasket, fix the rust which is almost certainly under the gasket, and then properly seal it.
Squirting silicone rubber in their will probably just trap the water in there and make it rust even faster.

Your description of the the "damaged" fan sounds suspiciously like a perfectly good fan to me; in other words, the shape of the blades is supposed to be that way. I believe the impeller type plastic blade is more efficient than the squirrel cage type.

You might get a little more speed out of the fan by lubing the bushings/bearings; the oilite bearing can be easily re-impregnated with oil if you have access to a small vacuum chamber. Immerse the bearing in a small container of warm motor oil and leave it in the vacuum chamber until the small bubbles stop coming off the surface of the bearing. The bearing should be good for another ten to fifteen years after that, at which time you can repeat the process again...

Bill