3 and 4 both sound like good options.

If 3, get a cover and a Hed 3 or Zipp 808 clincher for the front.

If 4, a pair of Hed Jet 90 clinchers with the PT could do everything.

1) Nothing wrong with this setup. Just take the cover off for training. As long as you have storage space for an inner tube and a spare tub, it'll be fine. You're more likely to puncture the rear anyway. I quite often race tubular front, clincher rear and vice versa.
2) No., you'd regret this option. See answer to 4 below.
3) If you're comfortable riding the Easton up front, I wouldn't reccomed this option. Besides, by keeping the Eastons you have a spare rear race wheel. This may be useful if you ever decide to try bunch racing.
4) No. You get a psycological boost from your race wheels, so training on them won't have that effect.
5) If you must change something, can I suggest you go for the complete clearout, as in your 4th option. Instead of getting dual purpose wheels, get a front race wheel and a front training wheel. Take the cover off for training untill such time as you can get another rear PT wheel. If you do a search of the forum, you'll come across a bike with a Zipp 404 PT rear wheel with a cover. That would give your race wheel, and your Mavic PT wheel could be kept for training.

Hope this helps.

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"Here's how you run a marathon. Step 1: You start running. Step 2: There is no step 2." - Barney (How I Met Your Mother)

Thanks for the feedback, I like your ideas.

As I will soon be riding a Real Design Aero HP fork, can anyone direct me to studies of tire/wheel/fork interactions for minimal drag?