Should I fire my store manager or let him stay?

Mid size family business. We employee about 25 people. Our store mgr has been w/ us for 6 years now. He is 60+ years of age and our highest paid employee with full benefits. He work production has gone down hill over the last 2 years. We have lost numerous amounts of staff member as well due to his lack of respect towards them, tone of voice and general work ethics expected. We have and had a wide age range of people working for us from 17-70. There isn't one associate that actually likes him. He is only worried about himself and his family. For me as the owner he is beneficial in the fact that he runs my store on a daily basis. He opens and closes 5-6 days a week. He is punctual, watches my $$ and reliable. I feel if I let him go he wont find another job, and then I will also have to pick up a lot of his slack. Working more hours, overseeing all daily duties, etc... What do I do? advise please... would love to hear