I am no bootfitter, but I have worn all kinds of boot and have had every foot fit problem a skier can have...
To me it sounds like the boot is simply too big, or the liner is complettely packed in. If the boot was comfortable at one point and you have more than 150 days on it then it may be the later. If was never ever comfortable then it is just too big. Typically the buckles, when secure, add only a little pressure if the boot fits properly.
Either way you are compromising for the poor fit by over tightenning the buckles, which compresses the foot down and out, cutting off circulation and rubbing your toes and the side of the foot into the sides of the boot.
Step 1 go see a bootfitter they will asses the fit and determine if the size is close enough to fix or if the liner needs to be replaced of if the boot is just too damn big.
Step 2 do exactly what the bootfitter tells you
Step 3 get back on the hill and rip it up.