About your 1st question, I thought that this post might be useful.
https://tanaikech.github.io/2021/10/24/converting-values-of-google-spreadsheet-to-object-using-google-apps-script/About your 2nd question, how about the following sample script?
const obj = [{ Name: "Joe", Age: 23 }, { Name: "Frank", Age: 45 }, { Name: "Sue", Age: 25 }];
const search = ["George", "Frank", "Jim", "Sue", "Bob", "Joe"];
const result = search.map(s => {
const idx = obj.findIndex(({Name}) => Name == s);
return idx == -1 ? 0 : obj[idx]["Age"];
})
console.log(result)