I use around 1.5g tea per 100ml and make three infusions with Darjeeling (well, with most black teas really): 2mins, 3mins and "a very long time" (IDK if the third should be even considered tea... I leave it be and then drink the resulting beverage at room temp)
I don’t have an exact science. I use about a teaspoon of leaves for a cup of tea, and steep around 4 minutes for the first infusion. If I use the leaves again, I’ll do 6 minutes the second time. If it comes out too light, I’ll resteep. If it comes out too strong, I’ll add milk.
I guarantee my method is way less scientific that it may sound :)
The timer habit comes from me forgetting about my tea about 50% of the times and ending up with an undrinkable cup.
As for weighting tea leaves... there's been a period when I felt particularly experimental and I was juggling some 8 different kinds of tea; I quickly got sick of remembering how many spoons of each kind I should use for my 300ml cup (density varies a lot depending on how much the leaves are rolled and how big they are) so I bought a 10€ "precision" scale and got into the habit of weighting my tea leaves.
Nowadays I generally have just two kinds of tea around (plus sometimes a third one I'm trying out), so it's not like the scale is really needed... I do appreciate the consistency however (I get tea in rather big bags, and the leaves on the top are noticeably bigger than the ones towards the end of the bag), plus having one less thing to remember is always nice.
Looks tasty. I drank darjeelings and ceylons for lunch for years at work. I used an unglazed ceramic easy-gaiwan, similar to what you have there. The unglazed clay softened the tea, so it didn't feel so harsh if/when I oversteeped it.