Fungicides are mainly preventative with some exceptions. They need to be on the leaves/fruit before the fungi show up. Some like Indar have a curative effect but that is the exception and the curative effect is limited. I know from experience that once cherry leaf spot shows up even on a small number of leaves it becomes much harder to control.
For the insects there are models that predict when the insects become active. I believe Cornell has some models available that you can use. The models take into account the temperature history to predict when the insects are active and when they hatch out. I don’t use them myself. For plum curculio there is a thread that talks about the temperature ranges when they become active.
If the temperatures are low the plum curculio can still be on the trees but are less active. I think most of us start spraying at petal fall or shuck split. And if the insects are there when the temperature spikes you can end up with a bunch of damage very quickly.
What insecticide are you using? Different insecticides are good for different lengths of time anywhere from 1 day to 14 days depending on the insecticide. I spray Triazicide at a 10-14 day spray interval. I understand you don’t want to harm pollinators but all of your trees are out of bloom right? So the risk to pollinators should be low. I would take all of the normal precautions, don’t spray when it windy, take care to make sure overspray doesn’t end up on flowering plants and mow down any flowering weeds below the fruit trees.