Wow! 100km’s using half a tank! Bad!
Does it drive differently at all lately, or is the fuel needle up & down at all when driving etc?
Maybe you could try filling it up again (make sure full) and seeing if the next half tank takes the same amount…and if it does and the gauge proves accurate then you could start looking into everything else!
You could always just swap another MAF as a quick test, but doing the above may help tell you if the gauge lies or if you’ve actually got something going on worth further diagnosing…