Some questions first:
1) What stove are you using? How many BTUs is it rated at?
2) What temperature do you have the thermostat set to? If it is reaching 75 degrees and still running full bore then you must have it set above that.
3) Where is the thermostat located, in the basement along with the stove or in the upstairs? Which area are you most concerned about heating and achieving a comfortable temperature?
4) You mentioned that the basement is finished. Does that include insulated walls? How is the floor finished?
And some answers:
1) There is no way to permanently adjust a lower maximum fan speed. CFM is an adjustment to control the minimum fan speed, but the top fan speed is full power and there is no way to adjust that. While the moving air may feel cooler than you'd like, the air still has the same BTU content in it and as such you aren't "losing heat" output from the stove in any way.
2) The automatic change from FSM to FSA is because the FR is so high. It is a safety feature to make sure you don't run the fan too slow for too long when the FR is high.
3) When the stove is running at FR 99, how much ash is there on the end of the grate? It is possible an adjustment to the MAX setting needs to be made to get the full BTU output of the stove. You should be getting around 1-1.5 inches of ash at the end of the grate on full burn. If there is more ash, then adjust the MAX setting in the SETUP menu up 2 or 3 points and leave it for 15 minutes. Observe again and adjust as necessary to get the right amount of ash at the end.
55lbs in 24 hours is a reasonable amount given the conditions you mentioned. Depending on the stove and BTU rating it may actually be a bit on the light side, if indeed it was running at FR 99 for those 24 hours. Make sure to look at #3 and make MAX adjustments as needed to get the full output potential of your stove dialed in. If you'd rather talk with us directly to discuss these adjustments and diagnose this issue quicker, feel free to call us at 315-299-3589.