Anxiety around eating out on the whole30 is totally normal! It sounds like you're doing all the right things by asking the restaurant about ingredients, cooking oils, etc. Restaurants are used to answering ingredient questions or making modifications, because so many people have allergies or intolerances. I think you can trust that they are making any modifications that you request (the last thing they want is a customer to get sick after eating their food). Also, seed oils are banned on whole30, but it's only suggested to limit canola oil at home. This rule is specifically because some restaurants only cook in canola oil, and the whole30 program understands that you may want or need to eat outside of your home sometimes! I don't think you need to start over after finding 1 corn kernel in your salad bowl. It was 1 kernel that you did not eat. Lastly, there is no such thing as a perfect whole30. This article is great to reassure that you're doing your best, and sometimes good enough is good enough. https://whole30.com/perfect-whole30/
Hope this helps! Keep up the good work.