Oh, okay. I thought it did. I don't multiclass, so I missed that it was different in the final product. Well then... your just screwed.
There is no possible way to play D&D solo without realizing the difficulty has been more than doubled. Even by level 5, a Goblin with a net or a Kobold Sorcerer with a sleep or charm person spell is going to have a greater than 50% chance if killing you.
The only way to play D&D as a solo adventure is to carefully omit certain combat tactics, have the enemies fight dumbly or just play only social adventurers...
Or create a bunch of NPCs to follow the main character around.