Howdy Dubois, I do agree with the others in that this could be tricky. Sinew is widely agreed to be a very good pairing with junipers and will definitely improve your chances of success. ERC is a fairly light wood and wide thin limbs are a good idea, but I'd still narrow the tips and get rid of most of that branch. Small, solid knots on the belly are ok, but can be fatal to the bow if present on the back. ERC can be heat bend so you might want to even out some of the bends as you get closer to final dimensions.
I've always opted to leave the back alone once I've stripped the bark, and end up with mostly sapwood in the bow. Other's have said they prefer to see more heartwood and remove some of the sapwood, or decrown the back. Since you're planning to sinew the back, reducing the sapwood seems like an OK idea, but it increases the work and increases the chances of problems ( ie. snap!!!).
Ron