taking a teaspoonful 2.25g daily really didn't agree with me
I've had other things that didn't work if I took them daily, but did work if I took them less frequently. I took a dose and then waited until it stopped working, and eventually came up with the minimal dose and maximal delay between doses. Occasional retesting is useful in case your needs and responses change.
i also drove 150mls - around 3.5hrs car journey the other day - which in the past would give me PEM and headaches - and i survived it ok.
Cumin didn't affect my baseline ME symptoms, but it did block the PEM, but I only realized the blocking effect when I did something that should have triggered PEM and didn't get PEM. You'll have to do something that will reliably trigger PEM, and then try it again after taking cumin (or any other potential PEM-blocker). Cumin did relieve the symptoms of PEM if I forgot a dose and then took it after. It worked within a couple of hours of taking it.
If it is actually working as a PEM blocker for you, please post that.