Ok, so...
I've received a lot , and valuable information in the
Sigil forum in regards to my original question. However, the problem remains that
Calibre is not allowing me to proceed with the conversion of the existing TOC.
I need help, Calibre-folk. Please.
If I don't use
Force use of auto-generated Table of Contents, my Kindle previewer (both local and online), will not detect or recognize any TOC. That is, the book (.mobi, or AZW) appears to not have a TOC.
If I do use this option, and use chapter detection, my title page is ignored and the book starts, with much "tweaking", in the copyright page.
I can sometimes scroll or navigate to it, but it's just not present as a first chapter, much less a start page.

Please, any suggestions, any help is certainly appreciated, and I thank you in advance.
BTW...I work with the Publishing house releasing this particular book, so I could very well upload any source material you might need, if that helps in any way. This is only my second eBook, and my first experiment with an image-as-chapter...so I'm not yet discouraged.