I think a solar sail mostly works at a broad reach or a run, so it would be more of a jibe than a tack ;)

I don't know anything about sailing but doesn't tacking depend on some sort of keel?

With a solar sail you can "tack" by reflecting photons against your tangential velocity – but that only works if the tangential component is indeed what you want to shed. Getting rid of radial velocity is more difficult, and in a hyperbolic (escape) orbit radial is mostly what you have.

Probably not at 540 AU. Not many photons out there for the solar sail to grip.