I think you are correct in working to low in the flame.
I am also self taught, no lessons here... I just figured out that I could make good twisties not long ago! I had just never thought of making them
OK so what did I do.. humm (now you are making my brain think! LOL)
For colors. I keep it simple. Start with one color, or group of colors like red or grey. then add one color, just one, any color that you like. Either you will like it or not
I also love to go to the paint section and get color starter room idea cards. The colors can be really inspiring, and right there for you already. A color wheel can be a valuable tool as well. Matching opposites or tri split colors that you can see are split evenly on the color wheel is helpful too and there are websites for this.
Other valuable color combinations can be found in your favorite picture, a color swatch, a makeup pallet, dish-ware, magazine pages, photo hoots, fashion, nature, picture books, web pages, stationary.. etc... There colors are already there for you, you just have to pull them together in glass
Stringer control, if you are on a HH start at the very back of the flame and bring in your bead and stringer until you are comfortable with applying the stringer. If you are on a oxy propane torch, I hear that working at the side of the flame, not in it works well.
twisties.. I sucked at these until i realized it was a lot easier to make them on the end of a mandrel as a punty instead of trying to do it on the end of a rod. I always got an uneven pull on the end of the rod, but the mandrel works great! For more twistie tips you can check out the twistie exchange thread too.
I can't help you much with murinni, I don't really use them.. I have a few, I am just not a big fan,
I am sure that you can find someone near Chicago to take a few hours studio lessons with someone. That may be better than a standardized class. You can work on what you are ready for. And probably get more than what you ask for anyways
. Then you can decide if a beginners class or intermediate class is right for you.