I mean this is the demo, that's why it's free. "Demo" doesn't mean playable in browser. And that's a deliberate decision on my part: almost all in-browser stuff plays like crap. Back in the flash days some of that would play ok (though even then it was hit or miss) but nearly every in-browser game on Itch, for example, runs like crap, especially if you don't have a high-powered system. This is a desktop game, meant to be played on a desktop.
If you're concerned about malware, caution is good and I applaud it, but I would point to the fact that I've been publishing and selling games here for several years now; I probably would have been banned by now if I was intentionally distributing malware. Unintentional is technically possible, but again, hasn't happened yet, and that's never entirely avoidable, even in the triple A space. If you're worried, do a quick scan before running it, but again, if there was an issue with the latest release, or any of them, people would probably have pointed it out by now.
I feel the pain expressed in your user name though. My password manager is a nightmare realm, and that's just the IMPORTANT accounts.