You might want to ask Schneider support for selectivity guidance. It might be you can change the 160A supply MCCB for a different model (e.g. 250A set to 160A 'In', or maybe going to one with 50kA or 70kA break capacity) or different settings to get enough for your MPB to LLPB requirement of over 5kA selectivity (on the computed PSCC current, more probably it would be L-E fault not 3 phase bolted fault so around half that PFC and OK).
I have spoken to Schneider and they just explained me how to use their selectivity tool on their website. I have tried most combinations and the maximum selectivity limit I can get between a 160A MCCB and 100A MCCB is 2.4kA.
If I were to change the 160A MCCB to a 250A, I would get a pre-arc error between the 250A MCCB and the 315A fuses at the cut-out which is why I am limited to a 160A MCCB downstream of the 315A fuses. Note that the pre-arc energy of the 315A fuses is 300kA2.
What options are there to reduce the energy let-through of a protective device? The energy let-through of the 100A MCCB is 327kA2 of the 100MCCB for the DB which is higher than the pre-arc energy of the 315A fuses at the cut-out: