1) Yep, might have to adjust it depending on the shape of the body you get (some bodies add more curves like muscles and some body fat).
a)/b)/c)/d) Both will work but if you're going to be mesh I do think you can manage to make your look work with also mesh hair and tail, I have some bento tail myself and I even saw bento lion tail somewhere in marketplace. Bento ears are also cool and they animate as well.
e) If you plan on buying a bento head, those usually come with tongue, and animations for it to "stick out" like yours does.
2) Yes
3) Animations work fine, your hand might be idle or in a weird position, but there are hand aos available.
4) Only prim clothing, no layers. Mesh body is applier or mesh only.
5) yes you can buy the body only and keep the head, but I seen some anthro full mesh that looks really good, you should give it a try. I'm a mesh defender