For German code, what is the correct fuse amperage, per phase, for a 3-phase service line?
I suggest you not to use fuses on 3-phase, just go for a magnato-termic breaker (L1,L2,L3 + N). Fuses have to be in fixture that if a single phase breaks, all 4 wires have to go out of power (if you have PE separated from neutral = both green-yellow and blue), or onlt 2 wires if you have a single PEN conductor.

Note that in tables usually they consider only 'active' conductors -> 5 wire cable is '4 poles' wire as PE isn't an 'active' conductor

PE = green yellow
N = blue
PEN = usually blue marked with green-yellow tape at ends and in accessible boxes