Checksum will change every time you make a change to the bin and save it in TunerPro. Automatic nowadays. Used to have to add hex...

I'm not sure how low min BLM can go? Really this is not a tuning tool, if your rich at idle take out fuel from VE table. 128 is the half way point of 156 bit so should be able to lower it? Honestly I don't know how it will effect the rest of algorithm of the ECM...

The " ----Fuel----" I think your looking at a title to separate things, not a paremeter, don't change it! In the next version of $42 they are marked as "Do Not Change!" Right click on it and Edit XDF, if the hex address is 0x00 it's a title, does it look like this? "-= FUEL =-"