Allowable current in Ni-Cr 80 20 gauge wire?
You can elevate the wire to Operating Temperature: 900°C

I believe this is a visible red temperature of heat energy levels.  The closer the temperature is to melting temp, the more fragile it becomes.



Melting temp:  Ni-Cr 1400'C  ,  Cu 1100'C

For straight wire at room temp:

No. / AWG)  204 °C  316 °C  427 °C  538 °C  649 °C  760 °C  871 °C  982 °C  1093 °C
      20    3.58    4.77    5.92    7.25    8.86    10.69   12.72   15.43   16.87 


The ambient temp of 200'C means you subtract 175'C then with a coil wire the heat rise per amp may be another 50'C. More insulation could increase this even more.

The bottom line is the wire temperature margin below melting.

Thus 650'C +250'C looks to be very close to the 900'C ideal working temp but geometric thermal resistance will affect your results.