The closest spread to peanut butter I've found in terms of flavor and texture is sunflower seed butter. It's also relatively easy to find; I've seen it in large chain grocery stores right next to the peanut butter.
A curmudgeon with years of practice. The bubbles in boiling water are steam or vaporized water. The bubbles initially do not reach the surface of the billing fluid as the colder water away from the hot bottom cools the steam turning it back to liquid. WHen all the water is at 100oC the bubbles reach the top.
The temperature continues to rise. Now, much water evaporates into the bubble on its way up; it expands, and makes it to the top. There the hot bubble steam bursts out into the air, and the pot's water temperature drops. Thus, the water temperature stays at near the boiling point of water. If I turn up the burner heat, I just increase the rate of bubble formation, bursting at the surface and cooling the remaining water by evaporation.