Grand Marquis Alloy Rims

I have a '93 Grand Marquis that had a flat on the back tire on Sunday. I jacked up the car, took off the lugs and couldn't for the life of me
get the wheel off the hub. It seems like whay they say about alloy and hubs fusing together is true.
I called AAA figuring they'll get it off. The guy who came couldn't either without destoying my room (he wanted to use a metal pipe to whack the rim off). So he just plugged the tire right on the rim. It was worth the few bucks he charged me.
So this leaves me with two questions.
1) In case I have another flat, or the plug fails, how can I get the wheel off? Can I whack it with a 2x4 (I get the 2x4 will be easier on the rim - the wood will gouge before the rim will - right?). Any other recommendations?
2) The puncture was a long nail that penetrated the bottom of the sidewall on the inner side of the tire. The back tires are far from new (over 7 years old) but still have a good amount of tread left (I only do 3500 - 4000 miles a year). They're Uniroyal TigerPaws (I forgot the exact model) if that's important. I've read/heard that patching sidewalls doen't work very well. The tire holds air and seems fine. But is the tire now weaker because of the plug in the sidewall?
I'm not opposed to replacing the tires. It would just be a shame to throw the tires aawy if they're still (safely) usable.
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