Not MY issues with your processes. SAFETY ISSUES with your processes.
First off, subzero cooling with a dry ice slurry should be done in something stainless. The plastic walls of an igloo can create a static charge with the alcohol and can potentially catch on fire.
Now we add to that a mason jar, with a loose lid containing a fair amount of butane, and we have a perfect recipe for an explosion.
I know you want to do the thing, and post your findings and this is all new and cool to you. But now that you KNOW, you can either take the information I have given you and adapt, or become another casualty.
One last thing, spend a little dime on a diamond miner and ditch the mason jars. Something my Dad taught me years ago, is that if you are going to do something, do it right. Save up until you have the money for the right equipment. You will have an ever greater sense of accomplishment, and you will be alive to feel it.