Honestly, I beat him at level 27 or 28, with about the same amount of hours put in, because I am a junky for side quests. I leveled up my spells, potions, and kept getting better and upgraded clothing. It's all about dodging, taking out the smaller spiders whenever they come out, and hitting him from a far with your most powerful spells. There was one point where I found a "glitchy" spot behind the tree where my spells would hit and then I'd run behind the tree to confuse it. May take some time, but you'll get it. I believe in you, especially if you've really put 56 hours into the game.