So... I'm not a Kossel expert. But I do want a Delta Printer in the worst way!

First, you are trying to adjust your height with the #define Z_PROBE_OFFSET_FROM_EXTRUDER in Configuration.h, right?

Comment #1: If you don't have Auto Bed Leveling turn on, I do not think the G28 command is going to factor in the Z-Probe Offset. Here is the only code in the G28 that references the Z-Probe Offset:

#ifdef ENABLE_AUTO_BED_LEVELING
if((home_all_axis) || (code_seen(axis_codes[Z_AXIS]))) {
current_position[Z_AXIS] += zprobe_zoffset; //Add Z_Probe offset (the distance is negative)
}
#endif

Your list of things you did also does not include a G29 command. Probably you should do a G29 if you do a G28. Without a G29 all coordinates are corrected against a unity matrix and there won't be any offsets factored into that correction.

If you have CUSTOM_M_CODE_SET_Z_PROBE_OFFSET defined, you can issue an M851 command to save new offsets in EEPROM. You can make adjustments up or down super quick. But my advice is not to do that. The distributed code won't tell you what the value of the Z OFFSET is with an M503 command. That was an over sight of whoever did the M851 command. It is a good way to get into trouble.