My husband told me that he doesn't want a runt because they have to learn as a pup to fight for their food and they become very challeging rather then a confident relaxed dog. Is this true? I don't mind if the dog is smaller but I don't need any behavioral issues espially since I have 2 other small dogs and 3 small children. What are your thoughts on the runt of the litter?

The runt of the litter can sometimes end up being the largest dog. If the breeder is good they will organize feeding times so that pups aren't fighting over food at all, I have found that sometimes the biggest in the litter can be the food possesive ones as they have the power to push the others out of the way.

Runts in the form of "teacup" dogs, where runts have been bred to other runts to try and decrease size I would highly advise against, but just the runt in a regular litter should be fine.

Like any pup you should start training as soon as possible and correct any bad behavior, no letting them get away with things because they are "just a pup", training starts the minute the pup gets home.