Your coyotes must not be particularly motivated because of good eating outside the fence. I knew a woman with an 8’ block wall, who was working in her backyard when a coyote made it over her wall, snatched her small dog, and with a running leap hurled back over.
Add to that the price of fencing 7 acres, and bullets are a whole lot cheaper.
I think you’re correct. Coyotes won’t make an effort unless they have to do so.
My fence (just measured it) is 7’ tall with spear points. Those pointed things would be painful in the belly if the coyote was impaled.
Concrete block walls aren’t much of a deterence and a wild canid or feline can leap to the top and then leap down.