I have used a C2 for years, but never developed a technical understanding beyond just getting on it and going for time and or distance. With a playful attitude, sometimes I'd go slow, sometimes I'd push hard. When my overall time or distance was done, so was I. ( I've been a numbers avoider and didn't want measurements to infringe upon my movement-fun-play.)
Now I'd like to utilize this great mechanism as a more transformative tool. (Seeking higher fitness levels and "lifetime" back/core prehab/rehab.) Accordingly, I'm sure I'd be well served to know some significant specifics.
In the FAQs and in many posts, one is advised to develop power at low stroke rates. I tend to keep the lever on the side of the fan between 1-4 ( mostly on the lower end,) as I understand this to be protective of the low back, again, a huge concern of mine and a major motivator in my wanting to "do" better with my erg.
My SPM are quite high, low to mid 30s and even higher. Does this mean the fan setting is too light ? Does it mean I am not pulling hard enough on each stroke ? If not, what does it mean and what steps do I take to improve and further explore this brave new world of "responsible rowing" ?

Also, does good technique call for an "explosive" pull and a "slow" return ?
TIA for answering these basic questions
Eddie