When a recipe calls for ‘individually wrapped caramels’, are these soft caramels (e.g. Jersey caramels) or hard candies (like werthers cream candies?)

The higher the temperature, the harder the caramel. That is basically the whole story. So I think what is happening to you is that the caramel in the middle is still going up in temperature due to residual heat, while the stuff at the sides cools down quickly because it can vent heat through the pan to the outside world. Have you checked the calibration on your thermometer? In any case, I think the things you can try are (1) cook to a slightly lower final temperature (back down a couple degrees at a time) and (2) set the pan over a tray of ice to cool it more evenly. Also, be sure to do a really good job of that final stir before pouring into the tray.

The sugar is crystallising. Try replacing the corn syrup with glucose syrup, or adding a little cream of tartar, both of which prevent crystallisation.