1) to edit characters, go to edit > characters and click max stats. it auto defaults lvl to 255 (note: hearts do not include heart containers/pieces of heart and I have no idea if it will register them for the achievement) 2) it auto detects dlc so as long as you have it installed, you should be...
Had the same issue, so I did a dual element weapon batch dump and found out...
Horse changes to Book of Sorcery
Spinner changes to Rapier
Rapier changes to Horse
Dominion Rod changes to Spinner
Book of Sorcery changes to Great Swords
Great Swords changes to Dominion Rod
The rest is normal...