The Hancock Moore website lists yardage requirements for each of their sofas,

And you can call for customer support.

There are different models of H&M City Sofa, there is a 9844 (larger) and 9840 (smaller) as well as a Sleeper version. Abount of yardarge will vary depending on your model. Faux leather is vinyl, and you will find it's almost as much as leather to recover in it. By "outdoor exposure" are you putting these outside the interior of the house? Or are you referring to sunlight in a room? These will not hold up outside, even under a covered or screened in porch. The foam will rot and wood swell and degrade, and the springs rust, they cannot go outside and last very long.

Reupholstering in leather will not be cost effective, you can buy new in the 9840 series for about the same price. However, the foam / springs / frame are excellent candidates for fabric re-upholstery.