Those measurements suggested that my initial correction to the Table 1 values weren’t quite correct, but a similar correction might work as long as I didn’t change the insulating wrap. This graph includes a linear fit to the Nozzle TC data, based on the original M2 firmware’s Table 1 thermistor data and cotton insulation:

Applying that equation to Table 1 produces this thermistor lookup table:
#if (THERMISTORHEATER_0 == 8) || (THERMISTORHEATER_1 == 8) || (THERMISTORHEATER_2 == 8) || (THERMISTORBED == 8) // M2 thermistors on RAMBO const short temptable_8[][2] PROGMEM = { {23*OVERSAMPLENR, 243}, {25*OVERSAMPLENR, 239}, {27*OVERSAMPLENR, 235}, {28*OVERSAMPLENR, 231}, {31*OVERSAMPLENR, 227}, {33*OVERSAMPLENR, 223}, {35*OVERSAMPLENR, 219}, {38*OVERSAMPLENR, 215}, {41*OVERSAMPLENR, 211}, {44*OVERSAMPLENR, 207}, {48*OVERSAMPLENR, 203}, {52*OVERSAMPLENR, 199}, {56*OVERSAMPLENR, 195}, {61*OVERSAMPLENR, 191}, {66*OVERSAMPLENR, 187}, {71*OVERSAMPLENR, 183}, {78*OVERSAMPLENR, 179}, {84*OVERSAMPLENR, 175}, {92*OVERSAMPLENR, 171}, {100*OVERSAMPLENR, 167}, {109*OVERSAMPLENR, 163}, {120*OVERSAMPLENR, 159}, {131*OVERSAMPLENR, 155}, {143*OVERSAMPLENR, 151}, {156*OVERSAMPLENR, 147}, {171*OVERSAMPLENR, 143}, {187*OVERSAMPLENR, 139}, {205*OVERSAMPLENR, 135}, {224*OVERSAMPLENR, 131}, {245*OVERSAMPLENR, 127}, {268*OVERSAMPLENR, 123}, {293*OVERSAMPLENR, 119}, {320*OVERSAMPLENR, 115}, {348*OVERSAMPLENR, 111}, {379*OVERSAMPLENR, 107}, {411*OVERSAMPLENR, 103}, {445*OVERSAMPLENR, 99}, {480*OVERSAMPLENR, 95}, {516*OVERSAMPLENR, 91}, {553*OVERSAMPLENR, 87}, {591*OVERSAMPLENR, 83}, {628*OVERSAMPLENR, 79}, {665*OVERSAMPLENR, 75}, {702*OVERSAMPLENR, 71}, {737*OVERSAMPLENR, 67}, {770*OVERSAMPLENR, 63}, {801*OVERSAMPLENR, 59}, {830*OVERSAMPLENR, 55}, {857*OVERSAMPLENR, 51}, {881*OVERSAMPLENR, 47}, {903*OVERSAMPLENR, 43}, {922*OVERSAMPLENR, 39}, {939*OVERSAMPLENR, 35}, {954*OVERSAMPLENR, 31}, {966*OVERSAMPLENR, 27}, {977*OVERSAMPLENR, 23}, {985*OVERSAMPLENR, 19}, {993*OVERSAMPLENR, 15}, {999*OVERSAMPLENR, 11}, {1004*OVERSAMPLENR, 7}, {1008*OVERSAMPLENR, 3}, {1011*OVERSAMPLENR, 0} }; #endif
I extrapolated the last entry from the previous two, because if the table doesn’t include an entry for 0 °C, then when you turn the heater off, the setpoint winds up being the lowest temperature greater than zero. Doesn’t make any difference, I think, but looks odd.
Load that table, run the temperature up, record more data:

The error isn’t particularly pretty, being off by +4 °C at the high end. You could hand-tweak the linear fit equation to push the error down at normal operating temperatures, but it’s close enough for my purposes.
Although I don’t have any numbers, one benefit of tighter thermal coupling to the extruder nozzle is greatly reduced overshoot during heating.