How many ants (please specify kind) and how long (hours) would it take
to eat 12oz of molasses?

The is not about ants, but I was helping a beekeeper friend extract
honey from 100 hives. Those bees emptied a 200 litre [ 44 gallon ]
drum of water in three days. We floated small bits of thin styrofoam
on the surface like islands, to prevent them from drowning, which
would happen if they "drank" while clinging to the vertical sides of
the drum. Interesting point. The more honey you got on you, the more
time they spent trying to recover it and the less stings you got.

According to this BBC article on ants
(http://www.bbc.co.uk/nature/animals/features/268feature1.shtml), a
swarm of 100,000 African driver ants can smother and reduce to
polished bone, animals such as chickens and even cows.  The article
mentions that it could take the swarm "a day or two" to eat a chicken.
 A cow could take "weeks".  If we estimate that a chicken weighs 3
pounds or 48 oz, then 100,000 African driver ants can eat about 1-2oz
per hour.

For your 12oz of molasses, it would take 100,000 African driver ants
between 3 and 6 hours to eat it.