Just to double check, your modded HBOOT is based on the latest LazyPanda 1.12.2222 HBOOT, not on the older 1.12.1111, correct?Attached is the fastboot-enabled HBOOT from the LazyPanda site, modded to appear as 1.19.0000, with build date updated, and red dev text removed.
As far as a hex editor goes, I use the Free Hex Editor Neo on Windows, and HexEditor on my device.