[jhowell]

I am not an expert, but here is my analysis.

Your CSS has problems. "width" is misspelled "widht". "vertical-align: center;" should be "vertical-align: middle;". Those should be corrected, but are not the cause of your problem.

Your use of the "height" property to control the height of table cells isn't recommended by Amazon. Amazon Kindle Publishing Guidelines version 2016.1, section 9.3.2 (Formatting Paragraphs): "The height property should only ever be applied to images in reflowable books."

It should work with newer devices, but older Kindles will display the book without your desired spacing. (If that matters to you.)

ETA: And if your book is converted to KFX format by Amazon, which is not under your control, it will automatically tighten up the vertical spacing. Trying to achieve a fixed layout in a reflowable book doesn't always work.