I've found that starting at a comfortable pace and gradually increasing my effort works best for me. No need to bank time early on, just focus on feeling smooth and relaxed. The goal is to finish strong, not to set a new PR at mile 5. Negative splits are all about patience and discipline.
Altitude training is overrated for most people. You'll get some minor benefits, but it's not worth the hassle. Just focus on putting in the work at sea level and you'll be fine.
I don't bother with heart rate or pace for recovery runs. If I'm feeling like trash, I walk. If I'm feeling decent, I jog. It's not about getting faster, it's about getting your legs moving and flushing out the junk from the previous hard run. Don't overthink it.