Bravo Jorge, glad to see someone else has a test running. I am getting about the same results so far with a few differences.
I have mixed D-76 and 1/4 filled some small plastic Pepsi bottles and some small glass drink bottles for a control sample. My butane is reacting the same as yours but my air/dev combo has not sucked the bottle sides in. Because of the concern about explosiveness of Butane I also have used a Dust off like product and it seems to be absorbing into the developer as the bottles look like they have been in a crusher. All samples still look clear but I am not going to open most of them till six months has passed. I am opening and re-butaneing (is that a word?) one of the bottles monthly.
I also have a plastic bottle of d76 1:1 in the fridge to see how long I can keep working strength solution.
This is so much fun I just sit around and look at the bottles for hours :twisted: