So apparently, thanks to you and other forums, this should be the solution :
Redirect my Click Track from Ableton to the outputs 3/4 of my BabyFace (is this the male XLR ones on the front ?) to the Audio IN of the SPD.
Then, the drummer will have to select PHONES in the Audio In settings so that the click is not routed to the main output. The audio In volume must be carefuly adjusted because it seems to saturate easily.
I’ll use the 2nd headphone output of my sound interface to hear the click too.
Hurray !
Well that’s just theory… I have to test this tomorrow whereas I don’t know my sound interface and that the gig is well… tomorrow !