can the MC only use appraisal on himself? If not why didn't he check out his mother at any point?
dude had an entire year, checking family members is like one of the first things you do when you are testing out appraisal. It is hard to believe he would not do it for a week let alone an entire year. Also she was in bed for a whole freaking year, and that also didn't make him think of checking her?
I am making a guess here, he never checked the stats of anyone else in his family after that, after all the manga would have shown it if he did. Based on how he didn't do it for an entire year, I think it would have been better if the MC could either only check his own stats or if he had to level it up to check other people's stats.
Right now it is like having flammable material over a candle you use often and then part of the house burns down and you say I should have dealt with that flammable material as you are lighting candles in other rooms with the same setup.