Part of your concern about the handling of your question is the way you're viewing it. You consider it your question about your own problem, and you should be free to do with it what you want if the situation changes. There's a lot of leeway for you to control your question as long as nobody else is affected, but it's not entirely your question.
It's somewhat the case that you contribute a question to the knowledge base in exchange for the chance to get an answer for yourself. You can contribute a question about a problem you don't personally have, or after contributing a question, you can discover that you need to ask a different question. Once a question is contributed, it becomes the site's question. If it is a valid question that could benefit others, your personal needs kinda become secondary.
Even though it's the site's question, you still have control over things like edits, to ensure that the question remains faithful to your intent. But your control has limitations when other users are involved. For example, you can delete it only before other people would be affected.
You describe contributing the question, offering the bounty, and then discovering that what you really need to ask is a different question. So ask another question. That doesn't invalidate the original question, it just means that you're no longer one of the people with a personal need for an answer to it.
Once other people are involved, a lot of considerations go into deleting a question. If the question is low quality or isn't of value to anyone else, and doesn't have any good answers, there may well be community support for your request to delete. But if the question is a good one, of value to others, or it has received an exceptional answer, the community would want a better reason to delete the question than the fact that you no longer need an answer for yourself.
This post in the help section covers the situation where you want to delete your own question: I've thought better of my question; can I delete it?.