To the level of quality that the linked website you provided appears to have, I’d say you’re looking at a year of work for a team of 6 composed of 2 juniors, 2 mid-level, 1 senior and one team lead + a PM and a UX designer.
But you can probably hack out a POC, maybe even something that gets you a first customer, where you’d give yourself 6 months for each of those features. Going that route, you’ll probably grow until your POC reached it’s tipping point, and then would need to hire that above team I mentioned to take a year to either rewrite or majorly refactor your POC so it can handle the next hundred customers and also keep your existing ones happy.
Similar to some other’s advice, I would try something called a spike. Basically, don’t quit your job just yet, but maybe try to take a 4 week leave. Then try to get the most minimal barebones version of one of your features going.
From that, you’ll have learned the complexity you’re looking at, the challenges, the difficulty, and your own velocity (how fast you make progress).
You can then decide if you should quit your job or not.
Addendum: Also, when you do that, when I say minimal, don’t take shortcut, you want to go fast (not worry too much about doing everything right and perfect, have the mindset you’ll probably throw it away and start over anyways), but make sure it is usable as a user in the way you plan to sell it. So like it should immediately handle someone signing up, logging in, and all that. It should be immediately deployed to a host or cloud, not just running locally. You want to make sure you’ve learned about the end-to-end challenges. What you can go fast on is code quality, test coverage, the UI/UX can be crappy and barebones, and only have a single basic feature. But try to make it like, even if that’s all it is, you could already have users signing up and using it in production.
If you don’t do that, you’ll get a very skewed impression of the real work involved.