Okay, I understand the main issues. I just don't know how to adjust the difficulty level, how much to increase it.
Regarding the boots, you get them right after the first interaction with the altar – there's a message that says so.
Only the last two lines worked from this snippet:
sleep(4);
PlayVisualEffect("/Effects/_(Effect)/Spells/Earthquake.xdb#xpointer(/Effect)", '', '', 119, 117, 0, 0, 0);
Play3DSound("/Sounds/_(Sound)/Spells/Earthquake.xdb#xpointer(/Sound)", 119, 117, 0);
sleep(2);
PlayVisualEffect("/Effects/_(Effect)/Spells/Earthquake.xdb#xpointer(/Effect)", '', '', 114, 113, 0, 0, 0);
Play3DSound("/Sounds/_(Sound)/Spells/Earthquake.xdb#xpointer(/Sound)", 114, 113, 0);
PlayVisualEffect("/Effects/_(Effect)/Spells/LightningBolt.xdb#xpointer(/Effect)", '', '', 121, 114, 0, 0, 0);
Play3DSound("/Sounds/_(Sound)/Spells/LightningBolt.xdb#xpointer(/Sound)", 121, 114, 0);
sleep(2);
PlayVisualEffect("/Effects/_(Effect)/Spells/Earthquake.xdb#xpointer(/Effect)", '', '', 124, 114, 0, 0, 0);
Play3DSound("/Sounds/_(Sound)/Spells/Earthquake.xdb#xpointer(/Sound)", 124, 114, 0);
PlayVisualEffect("/Effects/_(Effect)/Spells/LightningBolt.xdb#xpointer(/Effect)", '', '', 114, 121, 0, 0, 0);
Play3DSound("/Sounds/_(Sound)/Spells/LightningBolt.xdb#xpointer(/Sound)", 114, 121, 0);
sleep(1);
PlayVisualEffect("/Effects/_(Effect)/Spells/LightningBolt.xdb#xpointer(/Effect)", '', '', 114, 109, 0, 0, 0);
Play3DSound("/Sounds/_(Sound)/Spells/LightningBolt.xdb#xpointer(/Sound)", 114, 109, 0);
PlayVisualEffect("/Effects/_(Effect)/Spells/LightningBolt.xdb#xpointer(/Effect)", '', '', 124, 122, 0, 0, 0);
Play3DSound("/Sounds/_(Sound)/Spells/LightningBolt.xdb#xpointer(/Sound)", 124, 122, 0);
sleep(2);
PlayVisualEffect("/Effects/_(Effect)/Spells/LightningBolt.xdb#xpointer(/Effect)", '', '', 123, 113, 0, 0, 0);
Play3DSound("/Sounds/_(Sound)/Spells/LightningBolt.xdb#xpointer(/Sound)", 123, 113, 0);
PlayVisualEffect("/Effects/_(Effect)/Spells/LightningBolt.xdb#xpointer(/Effect)", '', '', 117, 111, 0, 0, 0);
Play3DSound("/Sounds/_(Sound)/Spells/LightningBolt.xdb#xpointer(/Sound)", 117, 111, 0);
sleep(2);
PlayVisualEffect("/Effects/_(Effect)/Spells/Implosion.xdb#xpointer(/Effect)", '', '', 119, 119, 0, 0, 0);
Play3DSound("/Sounds/_(Sound)/Spells/Implosion.xdb#xpointer(/Sound)", 119, 119, 0);
sleep(19);
StartDialogScene('/DialogScenes/Scena4/Scena4/DialogScene.xdb#xpointer(/DialogScene)');
sleep(3);
StartDialogScene('/DialogScenes/Scena10/Scena10/DialogScene.xdb#xpointer(/DialogScene)');
sleep(3);
StartDialogScene('/DialogScenes/Scena11/Scena11/DialogScene.xdb#xpointer(/DialogScene)');
sleep(3);
StartDialogScene('/DialogScenes/Scena12/Scena12/DialogScene.xdb#xpointer(/DialogScene)');
sleep(10);
SetObjectiveState("Prim1", 3, 1);
SetObjectiveState("Sec20", 3, 1);

Added 51 seconds ago
Try entering SetObjectiveState("Sec20", 3, 1); into the console before the battle

Added 30 seconds ago
Thank you so much for testing!