Using Fabian's data measured in 17614, I've obtained the calibration factors as follows.
Calibration notebooks can be found in /kagra/Dropbox/Subsystems/VIS/vis_commissioning/sr2/notebook/calibration/ 

LEN_HOR:
calibration factor: -115.477 µm/d.u.
linear range (5% nonlinearity):  ±67.785 µm

LEN_VER:
calibration factor: -106.598 µm/d.u.
linear range (5% nonlinearity): ±62.733 µm

TILT_HOR:
calibration factor: -706.673 µm/d.u.
linear range (5% nonlinearity): ±407.397 µm

TILT_VER:
calibration factor: -606.410 µm/d.u.
linear range (5% nonlinearity): ±338.377 µm

These calibration factors are implemented in K1:VIS-SR2_TM_OPLEV_{TILT, LEN}_{VER, HOR}_GAIN.