Please help in my first DSLR buy..

(Moving to this forum on suggestion)
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Folks-

I'm looking to buy my first DSLR, and here are my pre-conditions:
1. My budget is around $750.
2. I wear prescription glasses and I'm short sighted (-2.5 both eyes).

3. This camera is going to be kept for a long time to come. Not considering a replacement any time soon.
My shooting:
1. Primarily landscapes (all time of the day, especially dawn and dusk).
2. Family group activities indoors and outdoor.

These are the areas on which I need expert opinion:

1. Should I go in for a camera body that has image stabilization and auto focus? That way, will it open me up to buy cheaper lens?

2. I was trying out the Nikon D60 and Xsi yesterday. I could set the diopter in Canon Xsi to a level I need not my eyeglasses. But, with Nikon, I could not. But, if I prefer to have my eyeglasses on, is this a factor at all?

3. The Nikon D60 has only 3 AF points, while the Xsi offered 9. Should this be a factor?

4. Should I be confined to Canon and Nikon? How are brands like Pentax? Pentax K200d? How do these companies compare with Canons and Nikons, or should I stay clear of them?
5. Can I mix and match camera body and lenses? (from different makers).

I need a camera that will stay course with me as I learn more rather than just some Point and shoot upgrade equivalent...

Please suggest me some good cameras that I should try out before making a decision.
Thanks for your time.