Been there with the frozen butter thing and it is so frustrating. My first two tries at croissants turned into butter puddles on the sheet pan and I could not figure out what went wrong. What got me was that the butter was actually too warm in spots and too cold in others, so some parts shattered and some just smeared right into the dough. Once I started checking it with a thermometer and aiming for that 65 range like you said, the layers finally started showing up. Three batches is a rough lesson but at least the next ones worked out.