Interesting copyright questions

Southwest Virginia Project
In the multitude of counsel there is wisdom.

The following are copyright related questions of interest to me. They are either of interest because they arise frequently, meaning that there's considerable confusion about them, or they rarely come up, but they raise important points. The "response" is simply what I think based on reading of copyright discussions on the web. Use at your own risk.

I have a work published before 1928, but it lacks a copyright notice. Can I place it online? Yes. For materials published prior to XXXX, copyright notice is required to secure copyright. For such works, absence of copyright places the work in the public domain.
I have a reprint of a work first published in 1920. It is now out of copyright, but the company that reprinted it placed a copyright notice dated 1990 on the inside title page. Can they do that? Publishing companies often add additional information to a work out of copyright, then place a notice on the work giving themselves copy-rights. Sometimes the new material is significant, (such as a new forward, or a revised index, but sometimes it is trivial (such as the identification of the new printing company. Some believe that this is done to give the impression that the entire publication is copyrighted. Such notice applies only to the new materials contained in the reprint; the original reprinted materials once out of copyright, can not be taken out of public domain.
I've scanned a copy of a 1920 work, and want to place it on-line on my website. I've placed a great deal of effort into this project. I want to protect myself from others who might place it on their own website. I've placed a copyright notice on this work. Am I protected from others taking my scanned and edited version and using them for their own purposes? No. Once a work is out of copyright it remains out of copyright, no matter what you do with it, or how you display it. Any materials added to the text (e.g., footnotes, introduction, new index, commentary, etc.) would be copyrighted once fixed in a "tangible format" (e.g., published in hardcopy or on the web), but the original 1920 material remains in the public domain.
That's not fair. Copyright is intended to protect an authors creative effort. Scanning or transcribing an existing work is considered to be a mechanical, not a creative, act. Materials that you add may be "creative" additions to the work, and could be protected by copyright. The original materials, however, remain in the public domain.