Battery Percentage is not working after flashing Xperia E Dual with Nexboost ROM
You must have read about the bugs listed on that page before flashing the ROM. The bugs listed are -


Battery percentage is weird at times (goes up and down). Battery life is ok, though. There seems to be a problem with the Poseidon Kernel causing this. Hope @UltraGamerHD will fix it sometime in the future.
A lot of people ask about the stock Xperia Themes. Well, they don't work. I already changed .pngs files in various apks causing the themes to no longer work.
Some apps force closes at times (Whatsapps, Gmail, Browser,etc..). Clearing the apps data, they'll work again.  


They did not mention anything about FM Radio.  

So the main point is you should wait until they release their next ROM (or) flash another ROM better than this.