Here are some options:
https://creativepro.com/when-indesign-ignores-your-leading-values.php

It’s a great question, but I don’t think there is currently any way to do that. Are you getting a TOC in your document to work? That was broken before. Might be fixed now:
https://indesign.uservoice.com/forums/601180-adobe-indesign-bugs/suggestions/32396368-links-on-toc-doesn-t-work

I encourage you to use the indesign.uservoice.com site to make requests like this.

The new zoom behavior is actually quite nice once you get used to it. But you can turn it off:
https://creativepro.com/gpu-support-and-animated-zoom-arrives-for-mac.php

It hasn’t been updated in a bit, but it’s pretty cool: https://www.id-extras.com/html-import-script

Can you describe why you want to import HTML into InDesign? What is your workflow?

Robert, how many of these illustrations are you going to make? If it’s just one or two, why don’t you just place each text frame manually? It shouldn’t take long to place the text.

It seems like you could also do this by just putting the text in a 2-column frame and then using text wrap:

You can load an image here by uploading it to an image sharing service, such as imgur.com or imgbb.com and then copy and paste the URL here.

I was confused because you said it was an EPUB file… but you cannot embed an EPUB in HTML (that I know of). What you have in your example is a “Publish Online” document. I don’t think there is any way to remove that gray area. You might be able to adjust the position of their html inside the iframe, though. You would use CSS to set the position of the content inside the iframe and the size of the iframe.