Yes, ductless are the primary coolings source for the majority of homes in many other countries, all of Euroope,and Asia.
The inverter driven units like Toshiba- Carrier, can have up to four indoor units, of various capacities.
http://www.residential.carrier.com/products/ductfree/index.shtml
Yes, though to attic is fine for the pipes and electrical,will need to draian the water,which can be down the wall,if you have a crawl space,or open basement ceiling, or a mini-condensate pump can be used.
Likely less than central,or near the same,with your plaster walls , etc.
For a little extra you can get heat pumps,that will heat you home,in all but the coldest of weather , in some ares all weather, for less the gas or oil ,in most areas, ddepends on local cost of each one.
Look for contractors the are listed on Angie's, as well as www.acca.org and www.natex.org .
I know that Cropp-Metcafe is a great company in your area.
Source: http://www.bayareacool.com