issues with images in pages to epub

I am trying to create a very simple mostly text book with a few images captioned throughout, the aim is to export as an ePub.

I am having issues with images All I want it for each image to appear with the caption on the same page. I have no idea how to size images within the program so that they don't appear huge/split on an ereader.

it looks fine in pages, I have created a paragraph style for the images spreads, and make sure make sure the 'keep with following paragraph' (the image captions) option is selected. I've also made sure the image is 'inline'

but when I look at it in a reader it looks like this:

with the caption on the next page.

also, some images are warpped in landscape position, for example:

All I can think of is that the actuall image size (befor I adjust them in Pages using the corners of the box) is too large? baecause it doesn't do it in every image. If so, what pixel dimetions are safe to use?