I think it would be 50% because it could land on heads just as much as it lands on tails. its a even chance it could land on whichever it chooses to.
Not a lot besides the fact that they are both mixtures in water, because a solution is a mixture in which the solutes ( solids) dissolve, and suspension is a mixture in which the solutes don't dissolve.
To me, this sounds like the Garter Snake is becoming more immune to this toxic chemical.