Is it possible for a high sugar content and lower water content to protect the product if the ph is above safe levels?

Yes, to a degree. It is primarily the lack of free water. With a very high sugar content, as in this recipe, there is little free water. So the bacteria cannot grow because of the law of water diffusion.

Water will always travel from high levels of concentration to low levels of concentration. So the water in the organisms is drawn out of them and bound up by the sugar rendering them dormant.

Dave

Wonder if I could sub Lyle's syrup or honey for the corn syrup in this recipe?
Nancy

Don't know what "Lyle's syrup" is but if it has a different water content than corn syrup you'd be increasing the risk. With honey you definitely would increase the bacterial risk just as you do anytime you sub with honey.

It is a safe recipe as is but IMO if you start subbing things in it you move onto thin ice.

Dave