Your questions are very beautiful and fall into our topic.
When we consider fats, are we including all fat in the ganache - fat from butter, milk, cream and cocoa butter?
When we consider fats for your situation, I only mean butter or either cocoa butter.
am sure your cream is 35% or higher already hey
Is the invert sugar is reducing the amount of water available to surround the fat particles, causing the ganache to break?
Correct!
- the inverted sugar reduces the amount of water as result it will increase dry matter of all your mixture (Inverted sugar contain 62% min of dry matter).
- Inverted sugar is a powerful anti-crystallization
- lowers the viscosity of the masses. more fluid ganache
- Modifies, softens and shortens the texture
Is the balance between fat and inverted sugar a ratio or percentage of inverted sugar to total fat?
I have on my hand professional recipes that contain only cocoa butter with no inverted sugar, some with butter 16% water only. some with just glucose! no fat.
there's no ratio or percentage to follow! its all depend on the recipe given. yet be careful switching to milk ganache doesnt only change the amount of cream only but all the recipe. (unfortunately for books available in market i didnt see yet 1 book given details of a recipe, so dont be surprise to add extras work to adjust it.)
Am I close to thinking right?
you are thinking right just remember ganache is most complex material to work with from all my pastry and culinary experience, ganache perspective from conservation, storage and in relation to texture to tempered chocolate is the hardest to understand and follow! I till today I try to improve my knowledge with it and create conclusions. what i want to say is dont give up you are dealing with the most complex matter here LOL.
Also when you adjust your recipe if you reduce or increase some raw material you might solve the problem and create another one! so your goal with ganache is to find the ultimate balance to satisfy conservation, texture, taste. its a line that goes trough all the beauty of enjoying a ganache.