A good cross section of commentary.
1. I have 28mm tires which I'll transition back to after I wear out the 25's
2. Based on our tandem experience I should have shifted to a taller gear as suggested above
3. Sometimes you just ride what's in front of you; heading downhill would not have been an attractive option
4. Running start on a 12% grade might be attractive for some young, fit and agile; maybe someone can post a video