 Here is the Python code for setting up a combined fluid-kinetic simulation using the DREAM library with the specified parameters:

```python
from dream.simulation import Simulation
from dream.species import Species
from dream.electromagnetics import Electromagnetics
from dream.collisions import CollisionFrequency, UltraRelativistic
from dream.runaway import RunawayElectronGrid, RunawayElectronSolver
from dream.dreicer import DreicerRate, DreicerNN
from dream.initialization import InitializationMethod, Isotropic
from dream.advection import AdvectionInterpolationMethod, FluxLimiters
from dream.grid import RadialGrid
from dream.solver import Solver, Nonlinear
from dream.time_stepping import TimeStepping
from dream.output import Output

# Create a new simulation
sim = Simulation()

# Set electric field strength
sim.electromagnetics.electric_field_strength = 0.6

# Set electron density
sim.species['e-'].n0 = 5e19

# Set electron temperature
sim.species['e-'].temperature = 1e3

# Add fully ionized ion species 'D'
sim.species['D'] = Species(charge=1)

# Disable hot-tail grid
sim.hot_tail_grid.enabled = False

# Set collision frequency mode to ultra-relativistic
sim.collisions.mode = CollisionFrequency.ULTRA_RELATIVISTIC

# Include Dreicer and avalanche
sim.dreicer.rate = DreicerRate.NEURAL_NETWORK
sim.avalanche.mode = 'fluid'

# Set Dreicer rate to neural network
sim.dreicer.rate = DreicerNN()

# Set initial profile
sim.initialization.profile = 1e15

# If runaway electron grid is enabled
if sim.runaway_electron.grid.enabled:
    # Set number of radial points
    sim.runaway_electron.grid.radial_points = 50
    # Set number of momentum points
    sim.runaway_electron.grid.momentum_points = 100
    # Set maximum momentum
    sim.runaway_electron.grid.max_momentum = 0.5

# Set advection interpolation method to use flux limiters
sim.advection.interpolation_method = AdvectionInterpolationMethod.FLUX_LIMITERS

# Set initialization method to isotropic
sim.initialization.method = Isotropic()

# Set radial grid
radial_grid = RadialGrid(magnetic_field_strength=5, minor_radius=0.22, wall_radius=0.22, radial_points=1)
sim.grid = radial_grid

# Set solver to nonlinear and verbose with a relative tolerance of 1e-4 for the runaway electron current density
solver = Solver(nonlinear=True, verbose=True, relative_tolerance=1e-4, current_density='re')
sim.solver = solver

# Include fluid effects
sim.fluid_effects.enabled = True

# Set time stepper with a maximum time of 1e-1 and 20 time steps
time_stepping = TimeStepping(max_time=1e-1, num_steps=20)
sim.time_stepping = time_stepping

# Save settings to an HDF5 file named 'dream_settings.h5'
sim.save('dream_settings.h5')
```