Getting two minus numbers from an incoming serial string

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2

I am trying to get two values from this that I can use to set the temperature on a Dallas DS1820 sensor.

That makes no sense. You do not set the temperature of a thermometer.

All those Serial.println() calls are just wasting time and FLASH space. Make them print something useful or GET RID OF THEM.

  MsgMob[15];
  MsgTxt[50];

Completely useless. GET RID OF THEM.

inchar is assigned a value on every iteration of the loop to copy the content of the text message. It is only used after the loop ends, so it contains only the last character of the message. The comments after the loop, about testing any character in the message are WRONG.