it might not be completely valid, but i feel like the best evidence based approach is to use tomatoes as kind of a proxy for cannabis when looking at research since the optimal growth conditions tend to be similar.
"Tomato plants (Lycopersicon esculentum L.) were grown in sand culture to study the effect of different concentrations of potassium (K) on the vegetative growth, yield and important quality traits of different tomato cultivars, including TSS, titratable acidity, vitamin C content and pH of fruit juice. Three K levels (low, middle, and high) of 200, 300, and 350 ppm in the nutrient solution were used and two cultivars (Floridat and Super Strain B) were compared. Floridat cultivars showed 23% higher total soluble solids (TSS) than Super Strain B and also showed a total vitamin C content (4.65 mg·kg−1 ), markedly higher than Super Strain B. Increased K levels in the nutrient solution resulted in increased contents of TSS, Vitamin C contents, titratable acidity and juice pH in tomato fruits. Higher yield was recorded with Floridat cultivar and high level of K concentration (350 ppm). "
this is from a paper titled "Effect of Different Potassium Levels on the Growth, Yield and Quality of Tomato Grown In Sand-Ponic Culture"
it seems to confirm what youre thinking about increasing potassium, the problem with excess potassium is it antagonises magnesium. this is probably less important in the last few weeks than it is in early-mid flower. the study had elemental ppm up to 350 which showed the highest quality and yield, however we need to take into consideration our growing medium and style (i.e. coco coir will likely require much less K due to it being naturally present).
I feel like running slightly lower temperatures (72-76f) is preferable as the buds form. its still within optimal temperature range for photosynthesis, and allows you to run lower humidity while maintaining optimal vapour pressure deficit (VPD). I feel like 65% humidity at the start of flowering and tapering it off to ~50% mitigates the risk of mildew/botrytis much better, of course humidity is very difficult to control so this may not always be possible.
you could also run much cooler lights off temperatures if possible (60-65f), this increases the production of anthocyanins if the strains genetics allows for it, resulting in beautiful purple hues on the buds.
your lights are great, it equates to a daily light integral of about 36 which is within the upper range for optimal conditions (assuming you arent using co2).
edit:
scienceinhydroponics.com
heres an additional evidence-based resource that agrees with the above study, suggesting higher levels (~300ppm) of K may be optimal under certain conditions.
