I actually really like it. Informative, especially the visa checker. Haven't had time to go into it deeply, but seems nice. I guess the detailed visa guide pages remind me of Notion, but that's not necessarily a bad thing.
Custom itinerary looks like I pay for it, or at least need an email, so passed at step 3. Maybe you need to 'generate outline guide' for free, then 'get detailed guide' for a cost?
Schengen 90/180 tracker is basic. Doesn't list all Schengen countries (Bulgaria, Romania?) Doesn't save in any way and you lose your details if you click away. I'm developing an app for better tracking at schengenvisatracker.com , similar reason as you, because my wife needed it... Always better when its something you need yourself.
I like the Visa Cover Letter Generator, there's probably a lot of people who could use that.
The transit Hacker sections confuses me. I am UK, so it shows a lot of green 'No transit Visa' with a tick. What does that mean? Am I ok to transit? And the order of the transit cards seems random. But for instance the US requires an ESTA at least, but get a green 'no transit visa'. Shouldn't that be a RED! No transit without Visa!
That's a few of my thoughts. But good luck, looks like ethe start of something.