Use the below custom CSS in your WordPress Dashboard >> Divi >> Theme Options >> General >> Custom CSS area to make the event page full wdith.

.tribe-common .tribe-common-l-container,
#tribe-events-pg-template {
    max-width: 100%!important;
    width: 100%!important;
}
h1.tribe-events-single-event-title,
.tribe-events-schedule.tribe-clearfix,
p.tribe-events-back,
.tribe-events-c-subscribe-dropdown__container,
.tribe-events-single-section.tribe-events-event-meta.primary.tribe-clearfix {
    margin-left: 10%!important;
}
div#tribe-events-footer {
    margin: 0 10%!important;
}
h1.tribe-events-single-event-title {
    width: 80%!important;
    max-width: 80%!important;
}