Thanks, man - I am really glad you got something out of it. I'll be thinking of you, and hope you do well. Remember to relax when it starts to hurt - that was the most important advice I gave you. The more it hurts, the more you need to "fight" it by relaxing. It's a weird juxtaposition of feelings, but it's the way to go. And speed up your cadence with the quick, shorter stride turnover when it gets really rough at the end. Good luck!
Thanks - Yep, I knew others might chime in about breaking it up differently, mostly due to USA 5k races being broken up in miles. I'm in Canada obviously; and we have km markers, so it makes sense to use them. If I was in the US, I would do EXACTLY what you do. 800m sounds perfect. IMO, only having 3 "markers" (miles) would be too long between indicators of how I was doing, and I would want to cut them in half, basically (800m) just like you do, and go from there.
Also, I know warming up is a very personal thing, and can see how you do it very differently. I definitely start to do long-ish pickups near the end of running the whole course before the race, but not 800m-1600m. More like a few 30 second long pickups to race pace. I do however, time my warmup to end very close to race time (maybe this is why it works for me). I would never want to leave 15 minutes or more! To me, the warmup is the "stretching" part of it. I will run the first two km's of the warmup at a very slow pace (for me, well over 8 minute mile pace if I am planning to race around 17-flat). In a perfect scenario, I will finish the warmup with 3 minutes to go. Funny how everyone is very different with the warmup aspect. Interesting to read your take.
Thanks to everyone else who read my post and made a comment about it - I appreciate it very much! This is a great, supportive thread.