Cute!.... great idea.
As for rejoining, superglue may work, but it really needs two surfaces which exactly match to work best.
Liquid clay is probably your best bet since you have some.
And btw, polymer clay never gets brittle
from too much baking.... quite the contrary actually; many clayers feels longer baking makes polymer clays stronger.
You don't say what brand
of polymer clay you used, but be aware that Sculpey is the weak polymer clay so it breaks much more easily in any thinner areas than Premo or one of the Fimos.
It also darkens more easily than the others while baking, so when you re-bake the figure to cure the liquid clay if you're using Sculpey, try to use your large oven and also drape the figure with a damp paper towel (to try to keep the temperature as even as possible on all parts of the pieces).
You could do other things to secure the pieces too though:
If you don't want to rebake at all
...drill a small hole in the bottom of the head (just twist into the baked clay with a tiny drill bit, or press in a red-hot safety-pin tip)
... insert a short piece of wire or toothpick with some superglue on it
... put a bit of ink on the tip then press it to the tiop of the torso in the position you'll want (to make a mark)
...then make another hole in the torso and glue in the other end of the wire (you can also put a bit of superglue on the joining areas if you want) and press together for 15-30 seconds.
When you make joins later, be sure to have lots
of contact area between the raw pieces to be joined (and press them together well), and/or use liquid clay, and/or use a small connector as above, etc.
There are more suggestions on making good joins when using polymer clayon this page at my site, if you want to check them out:http://www.glassattic.com/polymer/glues-Diluent.htm
(...click on Some Bonding Techniques
GlassAttic ...polymer clay "encyclopedia"http://glassattic.com/polymer/contents.htm