Once you have a nice fluid sim and want more particles, you can double the particle amount and reduce the particle mass by half.
Viscosity and Stiffness of 1.0 is the maximum for the selected sub-samples rate. Above 1.0 can be unstable, but in some cases will work.
To make honey harden try reducing the density plasticity.
For viscous fluids the density plasticity is key. The threshold of the density plasticity should be 0.0 to have a smooth natural behavior. Try starting with stiffness at 1.0 and then set the sub-samples. Make sure the ground stiffness is high enough and then adjust the density plasticity to get the smooth flow.
Tension is the adversary of the Decompress force. Lower Decompress values mean more tension bringing the particles closer together
The "6.3" in the SPH solver refers to which version of TP it was first included.
This is a non-physical force to hold the particle on a minimum distance (spacing).
These distances will automatically calculate from the smoothing radius sphere and the density given. Without this force the particles tend to make chains or flat, concentrated areas. The density should evenly distributed in the smoothing volume, but the SPH technique doesn't care about the position in the volume, so you can get the density with only single line of particles laying quite close to each other!
If you change the Spacing the Density will automatically re-calculate to match this spacing. If you change the density or the smoothing radius the spacing will be re-calculated. A good range of values for the Spacer Force is between 0.1 and 0.2, and below this range you will see the chain and clumping effect.