Q. How strong are their jaws?
A. In absolute terms, there is no good measurement because you never know how hard they are biting. That applies to most animals but we do know the relative strength. Devils have jaws of biting power as strong as a dog about 4 times their weight. So a 10 kg devil has as powerful a bite as a 40 kg dog. In this respect they are very similar to hyenas, particularly the spotted hyena
Q. What do they normally eat?
A. Devils seem to eat any meat that is available. This includes birds, fish, even invertebrates such as moths and tadpoles, frogs and reptiles, and other mammals such as wallabies, echindas, platypus, wombats; in fact almost anything that they might find. They do have preferences. Devils seem to very much like wombat. This is probably related to the rich fat content of the food. This is because not as much has to be eaten for the same calorie count. What is normally eaten generally reflects what is available. What is available does not always reflect abundance because some very common food might be very hard to get whereas some rare food might be very easy to get. In wilderness areas where there is not much carrion, devils hunt a lot. Small ones hunt moths, tadpoles, frogs, ground birds, anything they can catch. The larger ones hunt correspondingly larger prey - wallaby joeys, wallabies, even wombats. There are records of adult devils catching adult wombats. Any incapacitated animal trapped injured sick is likely to be killed even if several times the size of devils. Most predators work like that. Animals are killed mainly to keep them safe or still while being eaten.
Q. Do they eat stock such as lambs and sheep?
A. In some areas, particularly farm land, much already dead stock is eaten. Generally dead cows can only have small bits eaten - the udder, the mouth, the anus - because the skin is too thick for devils. Whole sheep can be eaten except for the large bones. Any small stock like sheep or lambs that are injured or incapacitated may be killed and eaten. New born lambs are sometimes at risk. If sheep have twins or triplets, weak members of the litters may be especially vulnerable. Poultry that roosts on the ground is also vulnerable. Most healthy stock is perfectly safe.
I want one. Tasmanian Devil bad! 
:o 
