Actually, do change the gradlew arguments. I had the same issue, and, in being in the best spot possible for wifi, got it to work with 1020m. If 2040 does not work, plug in to your Ethernet cable and allot 4000m in the bat file. DecompileMc is a big task, and I think requires internet. Heap size is how much memory/power you allot to whatever you want to do. I would reccomend not going over 4g of heap size, as then things get quite messy with maximum heap size allotments.