SE are oils that meet the requirements for 1971 to 1979 passenger cars and light trucks. Provides excellant rust, corrision and oil oxidation wear protection, with improved high temperature deposit control.
SF are oils that meet the rquirements for 1980 to 1990 passenger cars, light trucks and small engines.
Basically you shouldn't use an oil lower than SE although you would probably have trouble finding SD or older spec oil.
I think they are up to SJ now and it is safe to use in your engine.
I use Mobil 1 10w30 in all of my 4 stroke engines, Kawasaki, Kohler and Briggs.
As far as the amount of oil to use in the engine just fill it until it's full.
I would stick to a 20w50 in the hydros. They are very expensive to replace if you screw them up. You could add a hydro oil cooler to the system though.