Given a polygon of approximately 800 hectares in the same CRS as yours, a points density of
0.0001 points/meter yields the following:
This is obviously too dense, as you've found. It should be noted that in newer versions of QGIS, it's possible to set your density parameter with much finer precision. Here is the same area, with a density parameter of
Which gives a mean distance of 235, very close to what you're looking for.
Given the limitations you're facing, though, it's still possible to calculate an equivalent result without changing versions.
Given that your area is known, you can calculate the number of points equivalent to smaller density values, and enter the result under the
Points count sampling strategy.
In this case, the area of my polygon * 0.000005 = 40.19. Entering 40 for the number of points yields the following:
Over a number of iterations, the results of
points count and
points density are more or less indistinguishable from one another.