Yep, intensity and spread is the better way of measuring for sure. 50k lux is 850umol/s so a dli of 36 over 12 hours, and 75k is 1275umol/s for a dli of 54. You want to be around 40-50.
The formula is lux multiplied by 0.017 to get PAR. Shane from migro tests it and it comes within a few percent of a par Meter.