Speaking to sandboxes and mini-games.
I understand that you like those features. I also suspect you want to explore those technologies with your game.
I'll advise you of the following. Folks here fall into two pretty distinct groups. Those who will play a sandbox and those who won't. Period. The second group won't even try your sandbox game, at least until it's hugely successful and maybe not even then.
Full disclosure. I generally hate sandbox games, but there are three out of all the sandboxes here that I play. Mist, Mythic Manor, and Lucky Paradox. The only reason that I even tried them was the continual appreciation expressed in their game threads. If not for truly incredible mod support for walkthroughs and other features, I would have abandoned them.
I'm here for Visual Novels. Novels that tell a story supported by imagery where I can make some choices and watch the story change. I'm utterly disinterested in finding myself before a screen with random opportunities to click and no context on how to proceed.
i appreciate you plan to have a walkthrough with each release to address that issue, but ask yourself the following question. Given all the work that you already see before you, is adding that additional work worth making a sandbox? As I understand your situation you are the only person working on this game. Which, by the way, has excellent imagery and more than decent writing. A traditional VN would allow you to focus on the story and the renders and animations to support it without the added complexity of a sandbox with mini games.
Anyway. As much as I think your demo shows the possibility of creating an excellent VN. If you produce a sandbox, you needn't "hope I enjoy it" because I won't be playing it. Two groups. Those that play sandboxes and those who do not, and the overwhelming majority of people who play these games fall into the second group.
Your game! Your Choice, which I fully support. Do as you choose, but please don't assume that your choice won't have very serious consequences for the size of your audience.