If you have access to every single particle in the universe and can put it wherever you want, and thus create whatever is theoretically possible for an almighty being to create, you will know how to fill all of spacetime with the largest possible amount of happiness.

What I got out of this sentence is that you believe someone (anyone?), given absolute power over the universe, would be imbued with knowledge of how to maximize for human happiness. Is that an accurate representation of your position? Would you be willing to provide a more detailed explanation?

And you will do that, since you will be intelligent enough to understand that that's what gives you the most happiness.

Not everyone is a hedonistic utilitarian. What if the person/entity who ends up with ultimate power enjoys the suffering of others? Is your claim is that their value system would be rewritten to hedonistic utilitarianism upon receiving power? I do not see any reason why that should be the case. What are your reasons for believing that a being with unlimited power would understand that?