Good question! Stink bugs and ladybugs are natural predators so attracting ladybugs with beneficial plants is very helpful. If you catch them early you can hand pick them off or vacuum them off with a shop vac or handheld vacuum. Mulch between plants which is a good idea always, but it can make it harder for the potato beetle to complete its life cycle. And then for splitting are you referring to the outside husk? If so, that is normal and it indicates that the tomatillo is ready to harvest.
