Yea, I ended up getting it with the Iron Pipe while doing my normal difficulty playthrough.
Also; the Icesaw counts towards the "Axe Chopper" achievement as well. Since that achievement unlocked for me while swinging it.
And for the "Master of the Nightmare" you can simply dashboard. I just held a controller in my offhand just in case. I only died about 5 times during my nightmare run. It just reverts you back to your last save.
Completed RPG's: 51
Proudest: Star Ocean; Dark Souls; Neverwinter