ipmiutil can also set the thresholds. See Supermicro fan control, IPMIUTIL or FEEIPMI? | Page 3 | FreeNAS Community.
List the fan thresholds:
ipmiutil.exe sensor -N <BMC host> -U <user> ADMIN -Y -c -g fan -v
It really isn't that difficult but you still don't have an IPMI device to talk to (/dev/ipmi0). So... reboot, if practical, to get a clean start and run:
reset; sudo modprobe -av ipmi_msghandler ipmi_si ipmi_devintf; lsmod | grep ipmi; dmesg | grep ipmi
Show us the output. And it's sudo...
It's for configuring over the LAN (-I lanplus). You have to replace nas-sol with your own hostname or IP address.
You can also run it as root on the server, which saves you some arguments:
ipmitool sensor thresh FAN1 lower 300 300 400
ipmitool sensor thresh FAN2 lower 300 300 400