You could try, but it will be a temporary fix at best and could plug up the heater core or radiator at the worst.
Nope prob leaking freeze plug
Water can not leak from the rear main seal, only oil. Most likely there is a leaking freeze plug near the rear main seal dripping water onto it.
Once it gets low on coolant because of the leak, absolutely. The leak by itself won't make it overheat if it's a small leak and your coolant level doesn't get low. If you DO have a leaking freeze plug, it WILL get worse, and probably rapidly. Also, if one freeze plug has rusted through and started leaking, you should replace ALL of them because the others probably aren't far behind.
NO
Sounds like a real bad idea. A leaking freeze plug is usually a sign of a very neglected cooling system. You need to replace the leaking plug with a new one. Unfortunately there is probably corrosion throughout the whole cooling system. You will probably have other leaks soon.
No
If it's out of a freeze plug you might want to take care of it yourself. Sometimes if you don't keep good antifreeze in an engine the freeze plug will rust through and start leaking. Sometimes they just start leaking anyway. If you can get the old freeze plug out and get the surfaces clean you might be able to put in one of the replacment type freeze plugs. That part isn't too hard, it just depends on where the freeze plug is.
A bad freeze plug will leak coolant and cause the engine to overheat.
It is possible for coolant to leak out between the motor and transmission, if a freeze plug has been leaking. I had this problem on an old International Travelall I had. The motor will need to be pulled.
More than likely your freeze plug is going to be the culprit and I would suggest you look there first. On some vehicles, the freeze plug is covered by the transmission housing or just plain difficult to get to and inspect for the average person. On older models, the freeze plug can rust out and create a leak. In this case take it to your trusted mechanic for repair.
A leaking gasket, a leaking filter, or a leaking drain plug....
There are about 8 freeze plugs which one is leaking?