Ram Gopisetti
Ansys Employee
LSDYNA has more capabilities in modeling direct human skull with Brain (SUFEHM) You can also do via THUMS and collect the injury HIC variables along with the pressure inside the brain.
your approach
i have implemented two methods, Lagrangian,SPH
i have used SPH as it was tailored to address Fluid structure interactions and you can expect large deformations as well( as the formulation will allow for it)
my probe locations are as follows

my results of pressure using the pressure as expression are as follows
you can reduce the particle size for further refinement you can tune the curves.
your questions
1)ALE is also suits for these simulations involving the fluids interactions.
2) perhaps, your material model is not good enough, try with inbuilt materials (WATER, WATER2, WATER3) in explicit dynamics library
3) LSDYNA does a good job as alternative to explicit dynamics.
4)you don't need such elements but you can explore.
cheers, Ram