When you finally release this on Steam, please include Steam achievements!
Also, any idea on the state of development? Do we have months or years left until product finished and I can buy it?
Steam achievements will very likely be added as that is the main reason the in-game achievements were added in the first place.
There are way too many factors for me to be able to predict an actual date so the only thing I can say about a release date is: It's done when it's done.
Sorry if that's not the answer you're looking for, it's just the truth.