fuel gauge problems

I have a 2015 F-350. Purchased it new 5 years ago and had a 50 gallons Titan tank installed at that time and had the computer reflashed for the new tank size. Last week My fuel gauge read below 1/4 tank and I went to fill it up but it only took 23 gallons. The fuel gauge is working, ie...

I have a 2004 f250 6.0 crew cab. When I bought it the fuel wasn't working (stuck on E with low fuel light illuminated) they said Ford had diagnosed it being a bad sending unit and parts were already ordered so I went ahead and bought it. Dumb idea I know. 5 days later 2 fuel injectors went out...