Gmhigee, you have a wonderful understanding of the dynamics. I so appreciate your expression.
You probably already know that hearing loss begins at the high tones. When speaking more loudly it is common for people to raise the tone. With hearing loss it is easier to understand when people separate the words, speak more slowly, lower their tone, and face the person they are speaking to. If you turn to him and touch his arm or shoulder, you'll have his focus without commanding it.
So few of the things we say are more important than honoring the person we are speaking with. It helps to answer each time as though you are telling it for the first time. People with hearing loss sense the frustration of people they speak with and it makes them reluctant to acknowledge that they can't hear.
You are teaching more with this post than you are likely to learn.