You shouldn’t have to mess with any PHP files to get these themes installed (that’s pretty weird that error comes up with your hosting). I’ve personally installed most of Appfinite’s themes (plus many others) with no issue whatsoever. What hosting company are you using?
Also, if you have FTP access, then you could easily upload any file regardless of the size to your site…..but you really shouldn’t have to do that just to upload a theme.
If your hosting company doesn’t provide any answers to how to get your themes setup, then I’d just upload them using FTP. That’s what all developers use anyways to install and edit new themes.