First comment: to use a source routine you need to active the SOURCE card which was not the case in your input file.
Second comment: If I were you, to avoid complexity, I you have rotate my target and the ursbin attached to it of 45d instead using the card ROTPRBIN.
If you really want to use a source routine, I invite you to use the source_newgen.f routine, which is easier to use. You can find it in the data base but I uploaded here: source_newgen.f (20.8 KB) FLUKA course, new source routine
Using this routine, you just have to modify direction_cosx, direction_cosy, direction_cosz
Please let me know if this solved your problem or if you need more.
Cheers,
Samuel