You can't sell potions to a merchant at a favorable rate, we intended it that way, right now the merchant works as a stopper. In the future he will only sell and buy herbs.
We get all the money only for the correct potions in the requests, but in the future you will be able to get money for all potions, but with consequences.
We have already fixed most of the problems, including saving. They work in version 0.1.08. It is now in paid access on our patreon.