Boots MUST fit.
If they are so bad... worst case, rent some. With renting, at least you can choose which fit best, and who knows you may find a decent fitting boot (or at least better than yours). Worth a try?
All that heel lift will end up hurting both your riding and your feet! if you ride a lot you can get blisters, plus all the extra effort to get response in a sliding boot will make you strain either the muscles or other parts of your foot. That sucks. On top of that... you will have to develop some funky techniques to compensate........ not good either.
You could also reduce lift without having to change boots completely (assuming the boot shell reasonably fits). Maybe go to a boot fitter, or try out thicker socks, aftermarket insole, jbars/cbars etc. Or even a new liner altogether. Sometimes even having the ankle straps on the bindings or the laces a bit tighter helps a bit..... it's a lot of different elements. Try all you can to see if you can get your boots to at least fit ok. Maybe like 1/4" lift is not the end of the world.
A quick "assessment": if after 4hrs+ or riding the first thing you want to take off are your boots.... something is wrong.