Tools\Options\Hatch and Flood\Min hatch area
You may have to change pour outline width as well.
I've increased the hatch area to 36 (6 x 6 grid). It works for flood "islands", as shown below, i.e. it is a small area with 2 partial connections to much larger plane areas. It stops it flooding.
It doesn't work for larger plane areas though, for example if you have 2 large planes (3rd picture below).
We need to keep the plane line width as 6 thou minimum.
What's the reason?
We do it down to 2 mil.
The PCB manufacturer that we use cannot work down to 2 mil.
Try setting "Split/Mixed Plane Smoothing Radius" to larger value maybe 3 or 5. Mine wont go above 5. I usually set to 0 to get fill into tight corners and get the connections like you have and don't want. Larger radius should get a gap with no overlap.
With a 6 thou line width, if you set "Split/Mixed Plane Smoothing Radius" to 3 for example, it will require 30 thou gap ((6 thou * 3) + 12 thou clearance (6 thou either side)). We can't do this as it will severely limit the flood.
The below picture (in outline mode - modeless command "o") shows a plane with a 6 thou line width. The smoothing radius is set to 5. It then needs 42 thou gap to flood through.
If you set it below 0.5 it does flood in more places, but you have the "partial" connections (shown in above messages).