can I run it in 14.4V mode and how can I do this?

I'd think that would be in the manual for the amp if it were really an option (as your specs seem to suggest).

Question about the speakers...

Do they require 50w RMS power, or is it just that they can handle 50w RMS power? Usually, I've only seen the latter in specifications. I've never heard of a regular speaker that required a minimum amp power. Unless you're talking about something special like a subwoofer driver.

If it's the latter, then 30w RMS will drive those speakers just fine. A 50w RMS amp will drive them louder and cleaner, but 30w will work too.