Obviously you want to add the ToC as a ToC entry treating it typographically different which makes sense. Your guidelines how the formatting should be are biased however (in my opinion). Including the page number seems quite obscure to me.
However, your starting point was quite right. You need to include the entry manually: but not using
\addcontentsline. This will employ the formatting used by every other ToC entry - which you are trying to avoid. There is a more general tool to add material to the ToC, i.e. write to the
.toc file which is the similarly named
\addtocontents command. You could use it like
To ensure the right page numbering the page number should be fetched with
\pageref and of course a
\lable right before
\tableofcontents. This can be done by patching the
\tableofcontents macro in the preamble and leave the document body untouched - which is convenient anyways.
Note that I used
\mainmatter in the examples (see below). They ensure that page numbering is different in the front and main matter which makes more sense if you want to have a page number for the ToC-ToC-entry. If you need roman numbering throughout you can omit those commands.
Moreover you could now use the above soultion to create even a different formatting: