For fonts, you probably need to add your own. See Changing the reader font without a hack [K3]
You may be out of luck for the RTL part. I'm not sure if MOBI even allows this - Windows MobiPocket Reader would likely be the best test. Even if WMR works, the Java-based MOBI Reader on the Kindle may have no support for RTL languages.
One option is PDF formatted for the Kindle's screen size, but I'm not sure of the best way to get there from (say) an ePub. You would likely need an embedded font in the PDF.