Post display not working right on browsers (but right in Customise)

I’m tearing my hair out with my blog’s posts not appearing right in browsers, yet it appears fine in the Customise when am looking at the post while logged in. All the posts are squishing up the bottom. I’ve tried asking the developer but they just said I’m trying to do too much (despite the fact I only have as many widgets are on their demo page before I bought the theme).
Any idea what code I might need to change? It seems particularly worse on all posts on Safari browser, but my latest blog post is also doing it on Chrome on Windows.
The latest post is here https://lifeisshortchallenge.com/helping-to-rebuild-nepal-on-my-challenge-4/