I can buy it for you, but I would either 1) need your email address for itch.io to send the gift to you, which is very inadvisable to post publicly here (so please don't), 2) preferably (if you have or make a Steam account), buy it for myself here (since I own it on Steam) and send you the Steam key or buy it and send it to you as a gift there (the gift, not the Steam key, requiring us to be friends on the Steam platform for three days to my knowledge), or 3) some alternative. In addition to all that, you would probably have to re-do all your progress, just so you know.
Progress is transferrable, but other than that, you're correct.
Downloaded Itch and Steam versions keep their saves in the same folder, so if you've played the download, it'll all just work. If you've played on browser, you'd have to export/import. The only transfer which doesn't work is you can't go from a newer version to an older one. So once you play on Steam/paid Itch, you won't be able to load that save into the browser or free Itch versions.