Site great on Safari & mobile - awful on Chrome & IE

Site URL: https://jtdemosite.squarespace.com/

Hi there, we are hoping to go live tomorrow with the new site but on testing it looks like we designed it on Safari and mobile - but it is awful on Chrome & IE.  Issue seems to be the way the margins are displaying on Chrome & IE plus the font sizing has been jacked up about  200% on those browsers compared to in design and how it displays on Safari and mobile.

Any ideas on the root issue would be welcome

Hi. Which elements? can you describe in detail?