I ran 2 different modules on 2 different workbenches.
I agree with the Pressure in and out boundary conditions - I came to the conclusion that for a given pressure inlet and outlet boundary conditions may not converge to a mathematically sound solution. I'm thinking of implementing a mass-flow inlet and outflow outlet BC. I'm not a huge fan of this combination because: 1) Not sure if this combination will be a good fit. 2) I won't be able to get values at each outlet face during postprocessing (or so I think).
As for the resistance coefficients - My end goal is to perform this type of simulation in an organ where the perfusion coefficient is extremely low (some references say these coefficients are even lower than the ones I've used: in order of e-13).