I'm fairly sure that these are NOT lantern flies, which are, well flies. They look like long-winged insects one might want to use as a fishing fly. Your critters are probably ordinary garden bugs (or bettles). Most beetle damage is from chewing, so holes, tears, etc are present. You might want to try a bactericide such as Bt. if you have damage to the plants you found the beetles on. The tomato problems may be verticillium wilt especially if the yellowed leaves are around the bottom of the plant and working their way upward. There is not much you can do to stop this .it is a soil borne disease that lives over in the soil. So rotate your plantings (3 or 4 years before returning to the same patch of soil currently used.) I have no answer as to what caused the yellow stickiness, perhaps some fecal matter from the beetles or bugs.