We cannot say for sure what is feeding on your basil. It may be beetles, caterpillars, slugs, wildlife, or something else. We cannot identify the green excrement (possible tree frog excrement).  Many leaf feeding beetles or slugs feed at night. You can go out at night with a flashlight and look. 

 If your garden is unfenced, you should consider fencing to protect against any type of wildlife. We recommend that you plant again. Make sure mulch is kept away from the stems of the plants. You can cover with a row cover to deter insect pests.

You can also experiment with planting basil in a container. 

Marian