Do I need a register my pseudonym?

There is no copyright protection afforded an individual's name, whether it be legal or a pen name. However, trademark protection may apply should the pen name become imbedded in the mind of the public to a degree that the use of it by someone else would cause confusion for consumers. This is a complicated area of law, and there is not a black and white answer without having more information. There are state and federal laws in place that may protect your pen name, depending on the state in which you live. It is unusual for a pen name to receive trademark protection, although it is possible. I highly suggest speaking with an intellectual property or entertainment lawyer so you can provide more detail and determine the best course of action. As for the "virtual" publishing company, as a general rule it is a good idea to have an entity in place to protect yourself from legal liability. If this "company" is not actually doing any kind of business, but is rather some type of marketing gimmick, I suggest speaking with your attorney so the two of you can flesh out in more detail what your goals are and how to best protect yourself.