Thank you very much for everyone who has pointed out the issue with the readability of the content. I'm very sorry for this issue.

Clearly your advice (px > %) is the way to fix this. I have to travel in a moment and the wp plugin I'm using did not support this, so will figure it out later today. In the meantime I reduced 150px to 100px, which seems to make the issue a little better for most screens (at least in landscape).

Thank you again, this is really helpful :)