Hope this helps...
1. Overland from Cusco, you can go by bus to Puno which takes about 6 hours (perhaps see Lake Titicaca floating islands from Puno to break up the trip, you'd need a day there) then onto Copacabana...unique border crossing into Bolivia over a river (included in the bus ride
) then onto La Paz from there. That stretch is about 8 hours by bus - option to stay in Copacabana though. La Paz to Uyuni by bus is about 14 hours in total - I stopped off in Sucre (was the capital, is pretty) and Potosi (silver mining town, where you can go in an actual working mine). Uyuni to Calama - I had to look in my guidebook as I wasn't sure where that was as I didn't go there, but now I see....you can go by jeep from Uyuni to San Pedro de Atacama, over the salt flats, and then onto Calama. I'm pretty sure that would be the only way to do it, due to the logistics of the salt flats. The jeep trip involves 3 days overland with 2 overnight stays in hostels along the way. It is really worth it (you can see in my "Big trip" link below if you like). I'm not sure on then getting to Calama how long that bit takes...
2. Yes, but you may need to pick and choose where you want to stop and what you want to see, based on the timings above. I'd recommend not missing the floating islands; La Paz capital deserves a stop (and the Death Road bike ride if you're adventurous, which takes a full day); the silver mines are an experience and the salt flat trip is fab!
3. Like I said, I haven't been to Calama, so I have just read about it in my guidebook just now, which describes it as a 'stopover' place - it doesn't sound like there's a lot to see/do there, so I would have skipped it, but I see you have your flight from there...perhaps if you find yourself in Chile with 2 days to spare, you should spend one in San Pedro de Atacama to relax after the salt flat trip, before moving on?
4. Is that the total cost for all flights in total, per person? If so, that sounds kinda right I think, although I bussed everywhere. You could perhaps compare the results with www.skyscanner.net and www.terminala.com