Nevermind. Had an extra 2 minutes and tested it.

When the max tech for Theo is listed in the table, that's implying what the 0.65 does in the formula. You always want to use the standard base, and let that 0.65 modify the standard base to the theo modifier.

i.e. =100+(83.33-100)*0.65*(1-EXP(-1*5000000/(780+5.75*10000))) = 89.1645