you want more light, get it closer. 3' is a long way unless it is an HID bulb or something.
depending on efficacy you can go up to 25-30w per sq ft. more efficient LED less watts per sq ft needed to give 35-40 DLI, which is ceilingn for ambient co2 - you dont need to go that high but you should definitely be over 22-23 DLI or you get mostly larfy buds. that's a grey area and not a hard line in the sane. too low and it gets larfy. YMMV may vary a bit per plant.
DLI is an easy step to convert your PPF reading. ppfd is the average over 1 meter squared and not a single measurement, fwiw. you can also get an accurate enouhg estimate of this just using light spec sheet infor - umol/s. Your distance from canopy sets the geometry to optimize your area of coverage. Best blanket of light without sacrificing too much under the lights (QB less distributed than bar or strip style light frames).
120degree beam angles unless there's something focusing the light. can use a 30-60-90 by splitting triangle formed in half, or use your light meter and make sure the middle doesn't drop too low while improving edges and corners. that's the height you want from plant. assumes you don't go over 35-40 dli, at which point you need a little less power or a bit more distance due to circumstance of context. more distance wastes a few more watts, but probably hits lower stuff slightly more -- not in a proportional way. definitely less efficient, yet better for plant slightly than reducing power.
Daily light integral - DLI - read up on it. wiki is sufficient. google DLI table to reference hours of use and PPFD to get DLI. again, just ballpark idea and needs plant observation and adjustments to fine-tune or push boundaries of 'max' relative to local environmental variables. without co2 added you'll burn the plant once you get near 40 DLI or above. sometimes this damage takes days or a couple weeks to be obvious.
you don't have to push "max" ... anything over low 20s DLI should produce okay buds. if you have a larger garden and need to cover it all. i'm not saying max dli is the most bang for buck ayield wise, but you'll get more a-quality buds for sure. light powers growth, so probably smarter to test upper boundaries before anything else.