If you could post your read-only link members can view if for you. However, when scaling up, so to speak. Simply add all your images to be larger for that view. 27" iMac, typically is going to be at or around 2500 x 1400. The largest, probably in the world, is 5120 x 2880. Now that’s not size, it’s resolution in “pixels”.
Therefore, your images need to start at: Minimum 4000 x 4000. I typically edit my photos from a very large 6500, 5500, etc which can vary. But try to keep them in that ratio, then optimized.
If you’re familiar with Photoshop, Affinity then you can edit and adjust the output size upon export.
Unfortunately, text is always going to present challenges when scaling up or down. That’s why using % percentages and VW viewport height for Typography text sizes is best practice, if you plan to have lots of scaling.
If you need further assistance, I’ll be glad to help get your photos sized properly, and adjust your text sizing to scale properly.