Depends on the amount/quality of the weed, the alcohol content of the vodka, the preparation, and the soak time. I’ve found some papers that claim 1g/1ml in pure ethanol is your upper bound (but you’re likely looking at sludge). Most countries define 40ml at 40% ABV as a “shot” so you’d probably want to have a similar sized “dose” and aim for 10mg in 40ml or about 187.5mg for the bottle.

It depends on what you start with. If you look at etoh tinctures you can get a lot of THC into a little amount of etoh if that’s what you want. If you are making your own with flower have fun experimenting and finding what works right for you. Otherwise, determine the potency you want, get some concentrate and dissolve it into the bottle until you get your dosage where you want it. As a reminder,you’ll need to decarb any flower you use and any wax if not using RSO.

Just put an f-ton of weed in there to saturate it and then dilute it as needed.

I’d aim for 5-10mg per 2oz shot. Seems that would be a similar buzz as 40% alcohol.