Is this jacket breathable? I have a HH jacket for heavy rain that is rubbery and not suitable for casual wear or spring travel.

The quick answer is no, However, it is rather light which lets heat escape with the hood down and the front open. To put this in perspective, I've been an owner/operator in the commercial fishing fleet in the Pacific Northwest for a long time. We go through gear like Denny's goes through eggs. I like some HH products. My advice is to use this jacket as a light layer for that mild mid 30-50 degree temp range to cut some wind and rain. It won't breath but it'll offer some comfort from the outside. Also, HH runs small. I guess they skimp in the Chinese factory to cut costs so its hard to layer. I wish they'd ask us (6'3"+ and 250 lbs) when they design new gear. Frankly, its okay for mild weather. To put it another way, no one is going to steal this jacket from you. Good luck and have back up.

How do I fold up or roll up and secure the hood on this jacket?

There is a velcro tab (approx. 3" long) on the back of the hood. When you roll the hood you pull or open the tab and it goes through a piece of material by the label (back of your neck). You then secure it back on itself

In this picture the navy color option looks very close to black.. can I count on the picture to be accurate with the color?

I never bought the navy. In the past I bought the mens black, mens yellow, womans light blue, womans white. The picure was accurate.

Iam 5.8 and chest 46 x large should be ok for me

What is your tshirt size? The jacket runs small. If you wear x large t-shirt like me, x large jacket is good. I originally ordered large, then gave to my 5 foot 5 girlfriend. I'm 5' 10. Wear x large shirts. I like more room in armpit. And don't like jacket to go up to my bellybutton, when I lift my arms up. No I'm not fat, I like jacket to cover me in rain