fill up issues

[daprotege5]

so im having issues at fill up, coincidence it started happening after putting seafoam in the tank. Have had one insistance where the gas guage stays stuck with the light on, the rest of the time seem to only get to 3/4 on the guage. Once my gas light turns on the max i can fill up with is 8-9 gallons. dont recall a time since ive got it that i can fill up all the way. Where would i start to diagnose this issue?? i see theirs a purge valve and the charcoal canister... my tank was hanging for a bit, fixed the straps thought that would have helped but still having the same issue. getting annoying to have to fill up so often when going on long trips.
any help is greatly appreciated.

 

[daprotege5]

So took tank out fuel gauge definitely looks fried. Fuel reader was saying 8 miles on display before taking out, needless to say tank is about halfway full and heavy as shit. Lol