Hmm, if you are using it for a quad, why not to take a flight controller with OSD? My RC plane uses a Matek F411-wing with OSD - a cheap 800TVL camera and a USB receiver dongle for my cellphone for FPV produces fantastic results in fact. I am planning for a similar thing to be done on my camera-enabled drone, and also on RC ships.
Alternatively - a wireless connection over something like HC-12 or ESP8266 module, or by using wemos mini. One arduino on the quad transmitting data, and another driving a I2C display on your transmitter to show data.
Actually my setup is now only used on a quite large slow sailing RC ship, and even there, I plan to install the flight controller with OSD for speed, compass, voltage.. No need for ailerons, only rudder and prop.