[SET_TL_GROUP:BY_CATEGORY:ALL:FLESH]
Here is your problem. You are telling it to set all the tissue layers to flesh.
EDIT: Also, you haven't defined FLESH properly (unless you have a material template called HARROWFLESH in the raws), so the game is taking the first material in the creature that is properly defined; that is, the porcelain. So it turns all tissue layers to porcelain instead.
What you probably want is this:
[USE_TISSUE_TEMPLATE:FLESH:MUSCLE_TEMPLATE]
[TISSUE_LAYER:BY_CATEGORY:ALL:CORE]
[TISSUE_LAYER:BY_CATEGORY:ALL:FLESH]
This will define the FLESH as being basically muscle, then tell the game to first add CORE to all body parts, then add FLESH on top of it.
Also take out these lines, they don't do anything:
[USE_MATERIAL:INORGANIC:CERAMIC_PORCELAIN]
[USE_MATERIAL_TEMPLATE:MUSCLE:MUSCLE_TEMPLATE]
[USE_TISSUE_TEMPLATE:FLESH:HARROWFLESH]
[TISSUE_MATERIAL:LOCAL_CREATURE_MAT:MUSCLE]
You can probably shear the flesh off, but you won't be able to eat it without preparation, since sheared tissues turn into body part items, not meat. However, if you add an automatic reaction to the farmer's workshop that takes body components made of the harrowed man flesh and then converts them into meat items of the same material, whoever shears the creature should produce edible meat immediately afterwards.
You can make creatures lay anything you want as eggs, any material or any item type all ready to use, but not if they are immobile.
Milking always produces a LIQUID_MISC item, which counts as food (if edible) and is otherwise useless by default. If you want to turn that milk into something else with a reaction, though, no problem.[/code]