Building to a heavy 2-rep first, expect to base the weight you'll use during the metcon off of that last 2-rep. The weight should be light enough that you can do all 7 unbroken quickly all 7 minutes. Strategizing the wallballs: yes that first minute will be your biggest set. It does not mean go unbroken. It should be a big set, and set you up for success in the later minutes. Something you could try to repeat. Today is an AMRAP, but one strategy could be to think of it as an EMOM. Decide how many you want each minute, try and stick to it. And there at the end, when you're nearly dead but not quite yet, pick up the ball and get 5. 5 is a doable number, so do extremely fast sets of 5. It's all about making it mentally manageable. Do that, and you'll be successful.