Maybe this is terrible logic but I would never trust an app that had 120 reviews and what appears to be a single person as the app owner with all my passwords.

No, I think that logic is completely fair. From my experience it is dead simple and works extremely well, however, I think it's definitely good to vet apps in your own way.

But who you gonna trust then? It's open source[1] at least, so you can always review it yourself.

But from "paranoid" point of view you can't verify is this is the same code used in app and all of currently available stores lacks in reproducible builds department. So it's always a tradeoff between ease of use and hassle.

[1]: https://github.com/mssun/passforios

Does that work as a password manager provider that you can enable for iOS auto fill?

Yes!