Hi, Shelly ... If your husband's been diagnosed with ALS, then those would be a natural progression into the bulbar area, I think. (I'm no expert on medical definitions, however.)
Yawning is part of it, and so is excess saliva (or reduced swallowing), which can lead to drooling. In my case, I have no "lip seal" left, so I drool when eating and drinking, unless I hold a napkin over my mouth. The "lip seal" is when we close our mouths so food or liquid can't escape. Weak muscles around the mouth can reduce the lip seal.
If he is choking, he should see a speech therapist or pathologist, to learn ways of reducing the choking .... this can be dangerous, and can let food or drink go down "the wrong way" and enter his lungs, leading to pneumonia. So let his neurologist know that he is choking.
Good luck to you both.