How can I have my text boxes in the name element longer?

Only by injecting the following custom CSS codes:

[data-type="control_fullname"] input {

    width: 100%;

}

You can also change 100% to a fixed value, like 150px.

Please follow the steps here to inject https://www.jotform.com/help/117-How-to-Inject-Custom-CSS-Codes.