Oops, I meant to write ? faster ?, not ? higher ?:
? If the earth's orbit around the sun happened to be slightly faster

it'd be Spiraling Away From the sun ( a bit more each year );
conversely, it'd be spiraling Into the sun. ?

Nope. You'd just get a different orbit. Once it gets into a particular
orbit, and no external forces or effects like tides act on it, it'll
stay in the orbit forever.

Thought experiment: Assume a rocket in a perfectly circular orbit around a
planet. The rocket fires momentarily to increase its velocity in the
direction of its motion. What happens? Assuming we don't reach escape
velocity, the rocket will still curve toward the planet but less so than
before. Its velocity will slow as it gets further from the planet (its
potential energy increases, decreasing its kinetic energy) until it
reaches a more distant point, when it stops getting further and starts
"falling" back. It will follow a path to the point where the rocket
fired. At this point it will repeat the path. Plot it and you'll have an
ellipse rather than the original circle.

NASA worked all this out years ago. It also shows a strange contradiction
of orbital mechanics: Try to speed up and you'll slow down (you'll orbit
with a longer period, further from the planet). Conversely, try to slow
down, and (assuming you don't hit the planet) you'll speed up by orbiting
closer and more often.

Spiralling away from the sun (or toward it) would violate conservation
of energy.

There is no need to be "perfectly balanced" other than perfect conditions
necessary to have a perfectly circular orbit. In real life, every bound
orbit is an ellipse, even if it's very nearly a circle.