Replying to Boot help/ shin bang +KARMA

i just bought a pair of the tecnica agent 95 s and i skied them for 3 days in a row

i got them fitted so size of the shell is not an issue

day 1 strapped them up super tight but circulation went dead and my feet went numb

day 2 strapped them up med and were fine skied nice

day 3 same thing but i started to get really bad shin bang

-my question is :

will loosening my boots all the way help stop this or give me more shin bang? should i go back to straping them up tight???

and how important is it to strap the power strap on top????