I'm sorry for all the rude, disrespectful, and harassing comments that you have been getting recently. From what I have read, I understand that you promised a Steam Key for those who bought the original content so that they didn't have to purchase the game again. However, I also understand that this was a misunderstanding of Steam's policies AND that you apologized for your mistake. While I understand why people are upset, there is no reason to fight and gripe with you about it.
Destroying a person's passion for making and sharing their games is beyond cruel.
I highly doubt that they will understand that though, as they are more concerned about the X amount of money that they paid is "going to waste." It is not like you were asking for a lot, just a few dollars to support the project. But some people are treating you like a large game studio that asked for x10 the amount of money, then made empty promises about a new update or sequel that turned out to be the exact same game in a new package. That is not what happened.
You stated explicitly that the steam version was not an update. You apologized for an unfortunate misunderstanding regarding the policies. You're even charging the same price for the game instead of up-charging it!
Some people enjoy being cruel to others, and sadly you became a target of that. And as you stated yourself, the majority of people who bought the game purchased it because they wanted it, not because they wanted to support you. Many of us understand that what has already been said cannot be undone. There will still be ignorant people that treat you like a farm for new game content, rather than a person.
Your community, the ones that realize that you are a person; the ones that respect and value your work, can only hope that you do not stop making games altogether. We understand if you need a break too. This situation would be hard on anyone. Hopefully it will all die down sooner rather than later.