Make sure both your on-site reservation and your pass is linked to your MDE account and you will be good to go for FP+ at 60 days.
You will get a confirmation number with your AP purchase that can be linked (if it doesn't link automatically). We just recently made FP+ reservations for our upcoming trip with APs purchased earlier this year. We will activate the passes when we arrive.
No. This year we purchased our APs before our FP booking window opened. They linked to our MDE account and I was able to do FPs at 60 days.
When we arrived this fall, I just went to a Guest Services window (could do this at ticket window as well, but we needed to renew TiW as well) to activate the APs.
Just be sure everyone with an AP is there and has a photo ID.