It definitely sounds like the strings were kaput.

Point 4 - could be actual difference as aged strings can corrode; I once sliced a fingertip sliding 8 frets or so up the neck on a pitted high E string (moral of the story has to be "don't attempt to show off on a friend's badly maintained guitar").

A really nice set I'm currently trying on a Telecaster is D'Addario EPS520 XL Pro Steels Electric, Super Light, 9-42. They give an excellent aggressive tone if I dig in with the pick, but can also give really mellow tones. A bit more expensive than Slinkys but I think worth the extra; I have no idea how long they'll last, though, as they've only been on for a couple of weeks.

They're also the same guage as the original strings on your guitar, so might be worth considering for next restring.

William MG. I completely agree on the quality of strings used by the manufacturer, BTW, and if freshly fitted probably sound like a guitar should :-)