1) 17mm hex head socket (to 30Nm, I think). You might be able to fashion a tool out of a 17mm head bolt and a couple of nuts.

2) No washers.

3) Yes. You can't use the stacked washers method against the rail without risk of damaging the rail. Use a bridge. But I guess it's too late.

Sixto
91 300SE
87 300SDL
83 300SD