I think you'll be OK. A number of guys have been using aluminum tape for this purpose. I suppose, with conventional tape, the adhesive just carbonizes and the tape is stuck in place by that.
The only way I know to positively control the temperature of a mold is with a thermometer. I drill and tap a hole for a thermocouple, but that's for aluminum molds with a poor emissivity. I think for a dark colored mold you should do pretty well with an infrared thermometer. Just pour at the same temperature every time until you find the one that works best for that mold, then keep using it.
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