That’s plenty of information to work with, thank you, and please excuse the delay.
This part is important. If you don’t have home switches, the machine treats the power on location as zero. I recommend reading this docs page: Machines without homing sensors or limit switches
And to consider adding limit switches to your LongMill MK1: Inductive Sensor Kit for the LongMill MK1 | Sienci Labs
As for the proper settings, it’s important to use the correct LightBurn version.
The version 2.0.02 you used still contains a bug that causes the problems you described.
An update with the fix is imminent. Until then, please use the Pre Release Candidate from here: LightBurn v2.0.03-RC4 Release Candidate
I’m pinging @goeland86 for further advice.