To be honest, I am way too invested already to not finish this thing, despite whatever response I get from posts like this. Sometimes I do get curious though. A surprising number of people I've asked in person simply are not interested in saving things from the internet. I guess if all you are into is watching Snapchat and Instagram all day, why would you?
This makes me think I need to tap into the larger business-type market and has me looking into what it would take to implement a permissions system for teams/multi-user editing of notes/etc.
No such thing. That's the sunk cost fallacy. But you probably already know that and are expressing your joy in the project instead of literal investment.
Failing faster and more often is a good strategy. There's a great Freakonomics podcast titled "Failure Is Your Friend" with a bit more context and justification.
If no one ever spends a dime on the service, you've always got one happy customer (yourself). Don't think about customers, build it for yourself and solve your own use case. If it's a good product, customers will find you/it. As soon as you get into tailoring it towards the needs of paying customers you've lost your original battle of creating something you enjoy for your own needs.