Jen - As I've said many times, understanding what the problems are and knowing what to do about them are two completely different things.
This last week was basically a recovery week - a couple of run / walks but nothing major. This was not completely by choice - I had yet another week of chasing my tail trying desperately to go back in time and find as much information on events that happened anywhere from 2 hours to 2 days earlier and my drivers chose not to report them. This included an obligatory drive around the county looking for more mystery objects that seem to cause damage to our buses when nobody is looking. At this point I would be content with a week that only had 3 Mondays in it.
Yesterday's run was postponed because both Andrea and I were not feeling great. Today we did a 15k and experimented with slightly different run / walk strategies. Part of the change in strategy was due to another bout of unusual wheezing - the wheezing was due to smoke in the air from a nearby orchard or field burning vegetation. This wonderful strategy ... Walk more up the hill so my breathing wouldn't be as labored under the more stressful parts of the run. The result ... the 15k took 4 minutes longer than our best 15k a couple weeks ago. I had more energy and had faster run segments during the second half of the run despite the wheezing issue.
Heart rate, sinuses and hydration were not an issue this week, but it was much cooler, a shorter run and i less horrible hill. Next week will be yet another longer run, but there will only be one hill to deal with.
As far as the question of what will I do if? ...
The odds of all those same factors happening again on race day or something less than slim ... especially the eating something horribly stupid the night before the run. However, if everything does go wrong I only have 2 choices - quit or try to finish.
Hydration is honestly my biggest concern. I sweat a lot - much more than normal people seem to and I always walk the fine line between water-logging myself and not drinking enough to function well. Being aware of how I feel and what my body is saying - taking the time at the water stations and so forth are the obvious solutions to this issue.
My sinuses are always a crap-shoot ... OK ... that sounds wrong :-/ Anyway, I always have some sinus issue going on so minimizing the potential impact is something I'm pretty used to. The wheezing on the other hand ... well ... if it continues to be a worsening problem I might have to visit my doctor one last time before June :-/
All I can do is keep doing what I'm doing. Prepare the best that I can and do the best that I can on the big day.