Minecraft – Wisp spawn conditions in Thaumcraft 4

You will need to return at least 2 villagers. Then they will start repopulating the village. As of 1.2, villagers will mate and repopulate based on the number of available houses. See this post (especially the "your village died out" section) for more information.

As of the 1.8 snapshots, though, the villagers need to be "willing" to breed in order to breed. It seems that you can make a villager "willing" by trading with them. Willingness is granted on the first new trade offer, and at a 1 in 5 chance per subsequent trade. Once a villager is willing, they will immediately seek another willing mate, if the village can sustain more villagers (based on the number of houses).

Jack-o-lanterns do allow mobs to spawn on them (so long as they can spawn at any light level).

Jack-o-lanters are both solid and opaque, allowing mobs such as slimes and pigmen to spawn on them. Compare this to Glowstone which is solid but not opaque (it is transparent), thus preventing spawning.

Unless they changed this since version 1.4, jack-o-lanterns are identical to regular pumpkins aside from glowing, meaning they are in no way, shape or form transparent. The fact from the Wiki on them being "partially transparent" is entirely incorrect.