1. Typically not very much, but it varies depending on the tour. Some tours I have spent less than I would have spent at home because I wasn't putting gas in my car.
2. I typically try to buy food close to where I will eat it to avoid carrying much. I often eat one meal per day in a diner and occasionally two. I cook simple meals.
3. I don't really train, per se. I do try to have some time in the saddle before a trip and be in a state of good general fitness.
4. I eat food that I like. It tends to be a carb rich diet.
5. I have ridden several different bikes on my tours. I ride the one that suits the tour route and my packing style for the tour. The following give you an idea of how flexible the possibilities are.
I rode a Windsor Touring (rebadged Fuji Touring) for fully loaded touring on my first long tour (Trans America). I used it for some other tours with medium and lighter loads on paved tours.
I rode an older (1990) Cannondale crit race bike for an ultralight camping paved road Southern Tier tour. I think I had 14# of ultralight backpacking camping and cooking gear. I modified the crankset to give me lower gearing by using a triple with the big ring removed. That gave me an "ultra compact double" 39/26 that I ran with a 12-28 cluster on the back. The whole setup worked fine.
I did an on/off road tour on an older (1990) Cannondale MTB with UL camping gear. I improvised a tiny rack with a small stuffsack on the back, a bar roll, and a little backpack. Base gear weight was just over 11 pounds and bike and gear together just over 33 pounds so the whole shebang together fit in a soft case that was airline legal and under the 50 pound limit. It was pretty cool to have a single bag that included bike, gear, and all to go on a long tour. Again it all worked out fine.
I rode a couple old bikes even though I owned a dedicated touring bike and truth be told may never tour on a "real" touring bike again. I am trying to make a few points. First if you learn to pack light you gain a lot of flexibility in how you carry your gear and what you ride. You get the joy of riding a more unladen bike. How far you carry this is up to you. You can go full on ultra light or you can just be a bit more careful in packing. Either way, I do advise you take great pains to avoid over packing. Second, you can get some experience trying touring on whatever bike you own.
After typing all that, I looked up the Specialized Vita and it looks like it is reasonably set up for touring. In hilly or mountainous country, especially if carrying much, you might want to fit a 24 tooth inner chain ring if it will take one.