Actually, there's nothing in the portions of the OPF you've included that looks wrong. You've correctly manifested the HTML ToC's file ("item"), the HTML ToC's id has been inserted into the spine ("itemref"), and a reference to the HTML ToC has been included in the guide section of the OPF.
Semantically, all is correct ... IF the physical file is truly named "TOC.html" (case sensitive), it exists (in the "Text" folder), and Kindlegen (Previewer) isn't choking on parsing it and its various links.
Do you get any errors/warnings in the build log?
EDIT: Also note that the "Copyright" and "Acknowledgement" references in the guide section of the OPF will not be recognized/used by kindlegen or Amazon devices. Only "cover," "toc," and "text" are valid reference types when building a MOBI/KF8 file with kindlegen/previewer.