I let the tiller determine the thickness. Yes, for pyramid bows the thickness should be pretty much even from fade to tip, but in the end, I don't measure it. I let the final tiller shape (I want) determine the thickness.
There are no rock solid tillering conventions. There are some ideal designs. Wood is a natural material with inherent flaws and characteristics. Tillering is not complicated. Believe what your eyes are telling you, have a set goal in mind BEFORE you start a build, and proceed with patience and diligence to arrive at your goal.
If I start out with a pyramid design, I'll floor tiller until I can arrive at a low brace, and then throughout the tillering process, I think round. Make the tiller round. I'll get the fades moving first, and then bring the tips around last so I don't end up whip tillered.
Reading good books is valuable, but it's like learning karate from a book. You can't... not well, anyway. Get your hands dirty (and you are) and experiment. Insanity is doing the same thing over and over, and expecting a different result.
Don't get me wrong, your bow is good, but with those stats and a good piece of wood, you should be able to do better with the set. Half that set would be ideal. I don't know about oak cuz I've never used it. Look at where your finished bows are taking set, and let it be a guide as to where the limb is over stressed. If your set is even throughout the limb's length... you're doing good. If it's all in one spot... you're not.
