When do I test?

I used two hours from first bite, as it seemed to respond to the alterations I made in diet most clearly.

Nuts and olives aren’t zero carbs, nor is the wine. Some nuts actually have a fair few. Better to not snack before the meal then add them to the meal itself. That simplifies the timing to 2130. Otherwise it does get a bit confusing.

You are testing your meals, so test just before eating a meal, and then two hours later. The usual aim is to have an increase of no more than two whole numbers. It is up to you what your base state is.
Personally I lowered my after meal levels to 8 and then stuck to that diet, seeing my levels continue to fall so that I now see levels under 7. I have two meals a day now, I eat early and late as that seems to be the best option for me.

I personally only think it matters if your testing the response to a particular meal to be as precise as all that. The first time i try a new dish, or push up the portion of carbs in a dish then i dont eat anything before and test 2 hours after a start eating.

In pretty much all other circumstances i just test every now and then a couple of hours after eating to make sure my control is not slipping.

I try not to make my condition run my life, i would go mad if i felt the need to test as frequently as i did when i first got diagnosed, i test in the morning some times, i test after meals some days.

I test before/after i eat something new frequently and in such circumstances i dont snack before.

In my opinion generally it is best not to snack at all. Eat a sufficiently satiating meal so you can get to the next meal without feeling hungry.
If you must snack and don't want to disturb your pre and post meal BG test results, the snack on something that is next to no carbs at all e.g. a large boiled egg is less than 0.5gms of carbs as is 100gms of Cheddar Cheese.

So far as timing of BG test(s) after a meal I vary it dependent on the content of the meal, so for some meals I may test 3 times:
For high(er) refined carbs, I test after 90min
For a typical Low carb meal, I test after 2hrs
For a low carb but high Protein meal I test after 2and a half or 3 hours (depending upon the timing of the next meal) - because Proteins do raise BG, just taking longer and lasting for longer like a carb spike on its side.