itch.io

That's awesome! I spent most of time for optimize static size version. When I made the dynamic size version, I realize the memory continuous and the neighbor query performance might be performance issue. Your implement handle these case will, nice and great job! :)

It seems you have some heavy task before you schedule jobs in your system. eg. allocate a large array. To figure out which piece of code takes time, you could use ProfilerMarker 
https://docs.unity3d.com/ScriptReference/Unity.Profiling.ProfilerMarker.html