There's one thing I don't understand though. When you are measuring your flavors are you pouring them in? If so, what's to stop from overpouring and screwing everything up?
Nothing

but your lack of attention. As I mentioned my droppers delivery right at .03g per drop. So I can use syringes to get me close on large volumes and then finish it off precisely with a dropper. If I am over a or under plus/minus .01-.02g I don't sweat it. Usually easy to get it within 1/100th of a gram.
The thing about using weight is repeatability and scalability. Volume is fine for baking cakes and cooking food but when making such small test batches and small bottles really overall the more precise you can be the better you will be at repeating the same results. Percentages are what is measured after mixing by weight when making complex formulations of various chemicals. No different here. I think I am just more science minded about it then most and I know I am a lot older than many here lol. Whatever gives you flavor you like and can repeat to your contentment works for me. You could use no unit of measure other than "it was about this much in the dropper of this, and this much of this" mixed with this and be happy as a clam.
As for my failures I have had a few that lets say are steeping still lol. I tried a frosted donut with cinnamon and bavarian cream just missed it totally. Also a waffle with pie crust and molasses and cinnamon. Pie crust is STRONG use sparingly. Got a few more I am putting together recipes to try next. Need to dump these donuts and reclaim the bottles. Will give them one more pass across the RDA but I don't think they are keepers.
My Sugar Bear clone is coming along nicely. I just adjusted down the vanilla custard by 50% to get rid of the perfume hint and it smoothed things out nicely.
Sugar Cookie CAP .9g
Vanilla Custard CAP .3g
Toasted Marsh Mallow TFA .6g
Cinnamon Danish TFA .75g
30mg/ml 50/50 nic base 1.93g
VG 12g
PG 10g
EM .1g
Make around 25mls of juice.
And if you use a dropper for making 20-30ml mixes it is super easy to get the weight nailed for each flavor fast. It doesn't take long to put a full gram into a bottle with a dropper. Using a syringe it is a pain and you risk putting to much if you overfilled. They are hard to push slowly for drop by drop like a bulb. Once you know the rough base weights of your ingredients and see what a certain volume will give you it is easy to then use a 5 or 10 ml syringe to pump in base liquids fast right below stopping. Same with flavors if you are making a big batch.
CC