Hi..filling is not at all possible as cavity is deep. Extraction is a good solution because its opponent on top is also not in good condition. Ideally teeth should come in contact with each other, but here upper wisdom tooth is badly decayed and lower has huge cavity. Removal of both is best solution. Regards

Carries is approaching pulp, though u don't have any symptoms right now but eventually it will pain so extraction could be your last option. If u want u can go for root canal of that tooth and save it.

The cavity is deep and quite close to pulp so it has to be treated..since your teeth has come out straight you have two options either to get it extracted or treated by root canal treatment..but the choice of root canal only finally decided by clinically seeing your case ..that is how good the accessibility to that area is..take care