So I'm troubleshooting what I believe to be fuel delivery problems. I filled it up and drove to work. Halfway home the battery was dead and it wouldn't start after I stopped to get a coffee (this is only the second time i've gotten the car to drive by the way so i'm still very unfamiliar with it). Put in spare battery, made it the rest of the way home (round trip 60 miles) and it never started again. Turns over but won't catch.

When I crack the injectors I can't get more than a drop. When I unscrewed the fuel filter I got a long loud hiss and could hear air getting sucked in and gas falling back to the gas tank. Lasted probably 30 seconds

Maybe just drove in on fumes and I didn't know? Gas gauge said I had only used 1/4 tank.

1) How big is the gas tank on a 240D?
2) What sort of gas mileage should I expect?

Also, when I replaced the fuel filter I found a metal washer that I"m pretty sure had been between the filter and its housing, the size of the bolt that holds it in. The new filter didn't come with any washers. The housing arleady has a rubber gasket. Should I be putting that metal washer in? I'm also wondering if I am getting air into my lines somehow and thought maybe this would be a reason?

Probably all pretty basic and stupid questions but you gotta start somewhere....