curious seekerji

I know that this is problematic because we have discussed it before.

Everything depends on context of use. One thing that is going to complicate matters is that the meanings of shabad and bani change according to the context in which they are used.

This is unavoidable in any language. Meaning comes from context. I can see that you have been consulting glossaries, making that suggestion moot in your case.
Reference:: Sikh Philosophy Network http://www.sikhphilosophy.net/new-to-sikhism/29471-questions-from-non-sikhs-to-sikhs.html

So to start this conversation, think of words that envelop other words, whose meanings overlap.

"A Shabad" in it specific context of Sri Guru Granth Sahib Maharaj refers to hymns or passages in the Guru Granth. The Guru Granth being a collection of shabads.

However "the Shabad" refers to all the spiritual wisdom contained with the Guru Granth.

On a more spiritual level "the Shabad" or "the Shabad Guru" is the complete message of Akaal Purakh revealed through His Grace to Guru Nanak and our other Gurus.

The Sri Guru Granth Sahib is now the Guru through which the Shabad Guru is revealed to us.

"Bani" in its more specific and literal sense refers to "word" and as Gurbani it refers to the Guru's word.

Gurbani - Definition of Gurbani - Guru's Word

So the Bani of the Guru is found, yes, in Sri Guru Granth Sahib. And in that sense Gurbani and Shabad Guru are the same thing.

Reference:: Sikh Philosophy Network http://www.sikhphilosophy.net/showthread.php?t=29471
In the large, the more mystical sense, Shabad Guru is something more abstract, and the source for the particular shabads.

Now the link that I posted above you will find some very helpful insights into Sikhism that are clear cut -- but in some cases they are too clear cut.