You were on the right track with the "kiss marks". Two beads touching and leaving an impression in each other or tacking to each other.
It can be a bit too hot without doing the whole gravity sag thing. I would recommend the external pyrometer you mentioned above. Artco has a good one for a decent price. Artco Pyrometer page
You'd put the probe in the kiln in the same location as the thermocouple and at the same height in the chamber.
Depending on the number of degrees of difference there are several solutions. Once we get some numbers we can make a clear plan of attack.