As for the sapwood/heartwood, the sapwood is better in tension, and the heartwood better in compression, sort of like yew. I've made A few ERC self bows that survived, leaving a thin layer of sapwood over the heartwood belly, but not many staves will allow this, since the sapwood/heartwood line tends to meander.
As far as recurving goes, I've never had much success in bending ERC, either by steam or dry heat. I know that it's been done, but I wouldn't get too aggressive with the curves.
ERC has a very low density, so go wide and long if you can.