Yes, you can use softeners on decals that have dried. I've successfully done it more than once on 1/43-scale diecast cars to improve the fit of factory-applied waterslide decals that were likely applied months or even years earlier.
In the last year or two I've bought quite a few 1950s and '60s car magazines at a kit/toy show in Milwaukee and at area antique malls. It's pretty unbelievable but the going rate seems to be about 50 cents apiece. That's asking price, not me making low-ball offers. I'm happy to get the ones I want, but it makes me wonder how the sellers find it worth the effort.
Have had some like that too, but where the blob stayed much closer to the can. Couple years ago I had a can of the Testors high-gloss clear that actually started spraying out of one of the can's seams. Made quite a mess even though I think I smelled it (and could hear it when I started trying to find what was causing the smell) within a short period of time. Pretty dangerous if you ask me, would be careful not to store any cans too near a possible ignition source.
The tubular pieces you are talking about are lifter knock outs. They are purposely created when the knock out pins are located close to the part, rather than actually on it. The resulting piece of plastic gives the knock out a place to push on and eject the part from the mold. At the same time, these "lifters" double as a overflow tab which helps make sure the part fills completely and that it doesn't have a weld or knit line where the plastic meets as it fills from both side of the part. It's very important on a part like that, because even it it was fully molded the weld line would be a natural weak spot that would easily break, probably as the part was removed from the tree.
Ron's Mundelein Hobbies is more of a train shop, but I was in the area and stopped in last week. It had been a while but I was pleasantly surprised how many car kits he had in stock and he seemed to have a lot of supplies too. The Hobby Town USA off Waukegan Road in Northbrook is decent too.
It is the '82 Mustang annual, but MPC really seemed to start downplaying the annual angle after 1978. They started giving most, but not all, the annuals "names" in 1979, like in this case Wild Breed. At least the first production run would have come with a plastic band around the box indicating it was a 1982 kit. My kit still has this. Presumably retailers could remove that 1982 band when the '83 kits came out, leaving a shrink-wrapped kit that people wouldn't expect to be discounted because it was last-year's model.
I think Brian is right that the SS badges were a from a pre-production plan, and the hottest '82 Mustangs ended up being GTs with 5.0 badges. I'm old enough to have built the kit when new, and I remember reading about the proposed Mustang SS somewhere and being surprised to see those emblems on the kit instead of the 5.0 markings. The '82 Mustang doesn't seem like much now, but I remember being pretty excited about it back then. Not as exciting as the '82 Z28 and Trans Am were, but it was still a cool car.
The hardtop version of the original came with one of the removable stock hardtops. It was one piece and the whole thing was molded in clear plastic. Kinda a neat piece, but it wasn't included in any of the reissues.