1: You can use any alchemy component for any of the processes that you have available. Those were examples listed of common components so you can get a sense of the types of things to expect.
2: Experimenting is a process that will always yield the same result if you use the same component. What is unpredictable about it is that from component to component the results are not tied to a mechanical formula. Each component is only bound by it’s lore based themes to determine what sort of experiment results it will have. Some of them get weird.
3: Those are just flavor titles to explain your combination of talents. I don’t specifically know what a hearth healer is but can ask Mike when I get a chance. Feel free to assign any lore based job title you would like that makes sense for both your character and your profession.