I didn’t even realise Airbnb had embed codes. So that’s handy to know.
Weirdly, I’m just doing some work to one of my airbnb rental sites, so I’ll for sure look at this.
I also use F3, so if I work out how to fix your issue, I’ll let you know.
EDIT: I’ve now got the code for my property, dragged an F3 column stack to the page, added two columns and dropped the code into each, using an HMTL stack. It looks fine, the columns are centrally aligned. Are you using the column stack in auto layout?
Go to your listing editor, click view, then in the popup click the share icon. You will get the embed code.
To be honest though, what gets embeded is pretty rubbish. It’s really just a small gallery and a link to the listing on Airbnb. You’d be better making your own little section.