try to convince the other gym users to buy a couple of barbell sets together?
anyway:
1. I guess you could, but it will be hard on the shoulders
2. sure why not, just keep the DB's as close as possible at all times
3.yes
4. try glute ham raises or any other exercise that that involves hip and lower back
5. yes, but you probably need heavy dumbells then
6. these are reverse pushups :
http://www.exrx.net/WeightExercises/...SupineRow.html
they work the back. you could do this or any other chest exercise :
http://www.exrx.net/WeightExercises/...tBenchDip.html
7. no, but you can do bent-over row with dumbells or reverse pushups to substitute for the cable row