I'm not really sure about this, but I think that guy did 120k damage is because of the Giant Growth rune which can give 15% chance to increase the damage of the next regular hit by 300%. (he used the rune before fighting niddogur)
His regular damage is 70k++ so a 120k damage indicate something abnormal is happening.
the best damage setup that I know of for HS : gungnir [2AK] EA10, +9 EMH & Ur's set. (my lvl 131 RK do 40-50k on egg with +7 EMH & 2AS instead of 2AK)
the problem with these setup is that you cant wear fire armor to reduce the damage from Meteor Storm. So modifying the setup above I exchange the Ur's set for Anti-magic suit [pasana], +9 FAW EA10 & Temporal Dex or Str depending on which stat do you 120 (enchanted with EA4 or Firelock card its up to you).
About bakonawa, I believe HS can reach him because I've seen RG can do Banishing Point on it. BP have 7 cell range & HS have 6 cell range so I think HS can reach Bako.
But the problem with this is that you are exposed to the Bako's regular attack which have 10 cell range. Which is the reason why some RK used Sonic Wave (11 cell range) instead of HS.
Rather than using HS+DB, its better to use HS+Sonic Wave like the video you posted.