It's not like these things are a Google search away or anything. Oh, wait. They are.
1. Working for a CEO is also absolutely voluntary; every single transaction is voluntary.
Yes, oppressing the working class is absolutely a voluntary matter.
Also pushing the same, tired misunderstanding and portrayal of Capitalism as "duh korparashunz".
Kinda hard not to when they're prominent in practically every aspect of modern life. :^)
2. The point is that there is a selfish motive involved with altruism, even though it is also not a reliable one. In fact, regardless of motive, the reason why Capitalism works is because capital is a generic means to the end that is a personal motive.
3. Again, relying on altruism. If you want to see if your vision would work, maybe try assuming no altruism at all, as a pessimistic ideology will handle reality better than an optimistic one.
How many times do I have to type the word "mutualism" to get that fact through to you lot?
4. Wouldn't that just be a type of governance, then (a.k.a. the state)?
Anarchism is about self-governance and abolishing unjust hierarchies. "Rules, but not rulers."