So…YES! IT WORKS! 
:
I can play any step of the Arranger, on the fly.
I mapped midi notes (Note number X, Velo Y) to
Stop (FC)
SPP (F2 X Y)
Continue (FB)
I tried midi loopback, but it freezed. 
. I’ll try to understand why later.
SPP values correspondance
BAR 1 - F2 00 00
BAR 2 - F2 10 00
BAR 3 - F2 20 00
BAR 4 - F2 30 00
BAR 5 - F2 40 00
BAR 6 - F2 50 00
BAR 7 - F2 60 00
BAR 8 - F2 70 00
BAR 9 - F2 00 01
BAR 9 / step 2 - F2 01 01
BAR 9 / step 3 - F2 02 01
…
BAR 9 / step 16 - F2 0F 01