I agree with Ross, replace the plug gasket.
Although they do not "wear out", if it's metal it's probably copper and they are made to be used one time and replaced. They are called "crush washers"
As they are copper and copper being soft, when tightened it conforms to any irregularities and no leaks.
But, when they are used once they become work hardened. The pressure from being tightened hardens the copper and when reused they do not conform as well.
The problem is, almost no one replaces them, and each time they are reused it's necessary to tighten the plug a little" extra" to prevent leaks. Eventually they leak, or you strip the threads on the bolt, [not a good thing] or in the pan, [a worse thing].
In a pinch, if you don't have a replacement washer, the old one can be annealed if it's still in decent shape. This means to heat the washer with a torch, [propane's fine] until it sort of glows red.
It won't get real red like steel, just kinda dark red. Then let air cool, do not squelch in water.
This makes the copper soft again, so it will conform.
If the washer has been reused enough it could be squashed thin as a razor, [not quite but you get the idea]. If this is the case it needs to be replaced.
Be aware some copper washers are not solid copper, but a composite of copper with a gasket type material sandwiched between the copper. These cannot be annealed.
Some washers are aluminum, these should be replaced.
I have seen plastic [nylon] but I wouldn't think this would be found on anything but a much newer engine.
I doubt the pan has rusted through, but anything is possible. It takes quite a bit to perforate an oil pan, and I would think you would have been finding "chunks" of rust for some time.
I assume you don't drain the oil from the plug, but suck it from the dipstick hole. Be aware that this does not remove all the oil so be prepared for quite a bit of oil to drain when the plug is removed.
If accessibility is an issue, one of the ratchet type wrenches might do the trick.
Just be very careful to avoid cross threading when reinstalling the plug.
Make sure, even if you can get only a few threads engaged, it turns smoothly. At the first sign of resistance, stop and make sure the plug's going in straight.
robj
P.S. If it's rusted enough that pulling on a wrench on the bolt "tears a hole in it", you really don't have much to worry about as the pan was shot anyway.