Then why did you get your DCCD controller fixed if all it can do is 35/65?
Go reread pages 15/72-18/75.
If you still don't believe it can lock up the entire differential to make a 50/50 split then so be it.
Yes, it does not engage when it is not required, and it slips some or much of the time depending on all the inputs, so what, that's what clutches do...
The clutch only has to act between two sets of gears, in this case, sun and planetary carrier. (P74) which are traveling within a a few maybe 10s of RPMs and only has to handle 15% of the engine torque to get from 35 to 50% front as the gears themselves are already distributing it at 35/65.
A car clutch has to handle 1000-2000-4000RPM and 100% of the engine torque. Completely different.