Check the gauge before you blame it. A welded-on factory gauge reads the air temp up near the lid, not the grate where your meat sits, so part of that 60 degree gap is just where the probe lives, not the gauge being broken. Stick a $10 oven thermometer on the grate next to a butt and compare it to the stock dial at the same time, then you know what you're actually dealing with. Mine ran about 30 off from the grate and the lid gauge also got worse once it was caked in soot, so a dirty dial can fake a drift too. Worth testing twice before you trust either number.

65 lb is the sweet spot for sure, anything heavier and my punch starts chewing up the edges too. For real big runs I bump up to 80 lb but only if I'm using a fresh blade, otherwise its a mess. Sounds like you got your setup dialed in now.

Learned this the hard way too, streaks in anything usually break the second you get comfy and stop paying attention. Same thing happened to me with a running streak last year, missed one day and suddenly it was three weeks off. The starter probably was not "finally working," you were just finally consistent, and day six you were not.