Hi. Sorry to hear of your suffering. I don't use heat at all. Just scratching gets the euphoric response for me.
I found relief from the intense urge to scratch by using Vagisil and now, Lanacane (extra strength). They have topical analgesics in them and as soon as I feel an itch that is in the intense range, i put on the cream and it cuts the itch before I succumb to scratching. I am not yet fully healed but i am getting close. It has been almost a year now since I would wake up as if stabbed by an intense knife of itchiness. I still do wake up itchy sometimes but i put a little analgesic cream on and go back to sleep.
These creams are not meant for long term use and they should not be used if the skin is really bloody. Having said this, they have helped me so much. I really felt like I was dealing with a kind of localized drug addiction. To me it felt like the heroin of itchiness.
Also keep your skin lubricated. Thick ointment-like creams are better and you might try one with emu oil in it as well as zinc. Having emu oil in the ointment really helped me to beat the dryness.
I am gluten intolerant and I find that eating wheat increases my itchiness in general. I am going to try a Candida cleanse and I plan to go off dairy again.