sorry for the delay. Life has been really busy with kids and moving, so I really haven't been able to commit the time to this project.
Regarding your question about the CO2 pressure low, you should be able to adjust the "Low Pressure Alarm" setpoint (and make sure it's enabled) from the mobile app.
That's strange that the calibration factor was just "lost". There is no way to manually re-enter that value. You can however re-perform the "high" calibration at your current known level. So if you know what the level was at, you can just re-calibrate the high to that level and the calibration will interpolate between the existing low cal point and the new high cal point. You wont need to open the lid or anything for this.
I hope this gets you going!
Also a shout out to @LBussy
for helping out while i've not been around HBT.