Currently we don’t support private networks in js-ipfs, and in go-ipfs it’s a very experimental feature so far. We might wait a bit for both the API and implementation to stabilize before we try to implement it in js-land.
However, I’m unsure of what you mean with “trying to bridge the gap” between your different nodes, what do you mean exactly? The swarm key is only used for setting up private networks. If you have public data but want less connections, you could always remove the bootstrap nodes and connect directly. That way, you’d only have a connection between your nodes, and that would be the full swam for you.