Regime estimation for parameter space of small system

depends. It can be better just because the cache is smaller though.

that’d be new to me.

Best thing to do is just try things. There’s a bunch of suggestions in https://diffeq.sciml.ai/latest/solvers/ode_solve/#Recommended-Methods-1, and yes try different tolerances.

If using pure DiffEq here, you can use https://diffeq.sciml.ai/latest/features/ensemble/ which will parallelize it.

sol.retcode == :Terminated

minimum is fine. Yes, it sounds like the equation could have bad behavior near zero, and extinctions in ecological models are definitely an example of this.

Not sure what you mean.