What you're describing is really bizarre to me, though, as it doesn't sound at all like the iBooks I know, which AFAIK supports vh, vw, and pretty much everything else that WebKit does.
Two things:
The reason your meta tag doesn't work is that it isn't valid XHTML by itself. You need a closing </meta> tag. Unless, of course, you did that and it still failed, in which case... no idea.
The spacing issues might be caused by a white-space or white-space-collapsing CSS property somewhere. Try overriding that and setting it to the normal value using a universal selector rule (* { white-space-collapsing: collapse; white-space: normal; }).
Beyond that, Apple has folks responsible for responding to iBooks-related bug reports from publishers and content creators. You can generally reach them by filing a bug report at bugreporter.apple.com. You'll need an Apple Connect account, but you'll need one to submit content via the store anyway, so you might as well set one up.
