1) 35 - 40.....whatever feels good.
2) The total length of the medium run should be 5-6 miles, but that includes warmup/cool down. The threshold portion of it should be between 20 and 60 minutes, in general. In your case, 60 minutes won't be possible because you'll go over your 5-6 mile limit. 20 minute threshold runs will be faster than 30-40 minute runs.
In the grand scheme of things, its not going to matter much whether you do 1.5 warm up, 2.5 threshold, 1.5 cool down, or 0.5 warm up, 4.5 threshold, and 0.5 cool down. There's no magic bullet here. You just need to run 20+ minutes at threshold. Personally I like to mix up the distances and paces, but some people prefer to do the same every week.
3) From the post that I wrote......oh, so long ago that I can't remember =)
"In Phase 3 many veteran athletes and elites have the foundation to run two solid workouts a week in addition to a regular long run of 18+ miles when preparing for these events. I feel that most athletes lack this foundation and are better served by running one race specific workout a week while reserving the second workout day for a second long run that is half way between your normal long run and your usual medium run (for example, if a normal long run is 12 miles, the second long run would be 10 to 11 miles). It would not be unreasonable for athletes with a little more experience to alternate their 2nd long run with a threshold workout. "
I'm not a fan of bricks, but if you need to do a few as a confidence builder, or to work the jitters out of your stomach, or to get used to the feeling of jelly legs, go for it. Again, it really won't matter much how you do it. Ride for 30 minutes hard, and then go for a 5-6 mile run. Its really that simple.
-----------------------------Baron Von Speedypants
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