Length of chain and RD question for 10 spd

[gongmech]

Ok clever hubbers.

 

I have some questions.

 

What length should the chain be on a 1x10 setup?

 

The reason I'm asking is that my rear derailleur gets pulled quite far forward and is under tension at the length that is recommended..( big cassette ring  to chainring.)

 

I also have installed an oval chainring. Doesnt the length depend on which part of the oval your chainring is on??

 

And lastly, with a longer B screw, the derailleur extends longer, but it still feels like its too short and if I look on the RD hanger, it looks as if it wants to slip off. Are RD hangers longer for 1x10 setups??? Something doesn't look right or feel right in this setup.