Hi, Michel.
Thanks for your detailed question.
I believe it’s because of your custom display not overwriting this pre-existing CSS from the Event Full Styles stylesheet (https://adventuresroom-mxeog07r.netdna-ssl.com/wp-content/plugins/the-events-calendar/src/resources/css/tribe-events-full.min.css):
.single-tribe_events .secondary .tribe-events-venue-map {
width:58%;
}
With that rule removed, it displays at 100%, which is what you’re wanting instead.
You could add this CSS that should resolve the issue for you:
body.single-tribe_events .secondary .tribe-events-venue-map {
width:100%;
}
Please let me know how this goes for you.