The low end of the usual range for finishing the game is about the low/mid forties. With the 5 level jump becoming the Divine One, you probably shouldn't have too many problems if you hit the gong in your mid thirties. If you use scorpion traps or a sword with Frost on it, you could do so earlier. It doesn't get harder in the wastelands, except for a few of the less common monsters (and then not by a great deal), so if you can walk around now with nary a thought for your safety, you're likely good to go for the wastelands.