I thought about 100k as the first reward, it's a big enough amount to make almost anyone interested. Maybe get your average daily wage and start from there. Working 1 day "for free" to conduct such a social experiment could be worth it!

You can't really sweep 50 sats because it's below the dust limit so you need to already own a UTXO for that and you'd be at a loss (need to spend ≈140 sat for a tx at least). Of course, 100k would result in too generous numbers if you double it every two weeks so maybe multiply it by 1.5 and only stick the next sheet every month or so. Or cap it after 1-2 mil. All depends on your generosity and the stranger's patience.

Thanks for your kind words!