Wrapping Text in Twenty Twelve

What happens when you use the unedited parent theme?

Same thing.

all header tags in Twenty Twelve are formatted with ‘clear: both;’ which prevents wrapping.

you could try to overwrite that for just that one page by adding this to the custom styles:

.page-id-205 .entry-content h4 { clear: none; }

or for all pages using the used page template:

.page-template-page-templatesfull-width-php .entry-content h4 { clear: none; }

or for the content in general:

.entry-content h4 { clear: none; }

Thanks! That did help but the clear now messes with the text:
https://ravenrooststudio.com/wordpress/exhibition-list/