I cannot turn the gas down very low on my burners without it popping off. What heat diffusers/flame tamers do you recommend?

If I need to diffuse a flame I often just move the pan to one side(offset it) letting the flame just barely touch the pot. No diffuser necessary. Just make sure the pot isn't in a wobbly position and that it sits solidly on the burner.

Really you can use a very inexpensive model and it will serve you well. I bought mine at the 99 cent store and it works great. Just remember to keep the wooden handle away from the flame!

I like the 7-Inch Cast Iron Heat Diffuser by Ilsa. I bought mine almost ten years ago and use it regularly.