No, Merit cannot be used in a vegetable garden for grubs. We recommend contacting your local cooperative extension for advice. These centers have master gardeners that are familiar with regional pests and regional vegetation and can offer advice on safe products to use in your vegetable garden.
We do not know the setting for that spreader and we are not sure exactly what to set it on. However, almost all fertilizers, herbicides, insecticides, etc have treatments in amounts of so much product per 1000 square feet. So if you can figure out what your walking speed is then you know anytime you apply any product that calls for so much of it per 1000 square feet, you always set your spreader on this setting. You can calibrate this by marking off a 1000 square foot (10 x 100) area and placing 1.4 pounds of any type of product of similar granule size, or of the merit itself in the spreader. Start with a low setting and start walking your marked off area at a normal pace. You can adjust as you go and find the basic setting for you to apply the product over a 1000 square feet. The 60 pounds per acre equates to 1.4 pounds per 1000 square feet. Or, you can call Bayer, the manufacturer, and they may be able to tell you what setting you should have it on. You can reach them at (800) 331-2867.