Take the day off. I believe most weeks you need one day off the bike and the day after a race is the best one to take.
(2) If you are indoors aim for the same workout intensity.
(3) The plan has endurance built into it. Stick to the plan and work on your race execution skills (pacing and fueling) to improve 3rd lap speed.
(4) The correct warm up for xc racing depends on how warm it is, what level of fatigue you have, the course profile (how soon does it bottle neck) and your comfort with the start speed of the race. So I don't have a generic one warm up works for every situation recipe.
One interesting study done a couple of years ago examined various warm up regimes with experienced athletes. The outcome was that comparing a light warm-up, a deeper warm-up and the athletes own self-selected warm-up, the highest performances in a subsequent test were from the self-selected warm-up (which differed for each athlete).
Interesting stuff.
Lynda