I strongly disagree, for one simple reason - you have two stars, one on the edge of the circular field, the other positioned such that half the mass is inside it's orbit, the other half outside it's orbit. That mass is finite, and so is the gravitational attraction towards the center. Nothing goes to zero. Nothing approaches infinity.

We're dealing with finite entities, here, and the model is patterned after, and close to, our own Milky way. Clumping doesn't enter into the picture, nor do the spiral arms, because it's at such a distance, and there are so many clumps and arms, that while these might cause pertubations in our orbit, those are minimal unless we get fairly close to a clump. If that happens, then, yes - we might get tossed outwards (slingshot) or decayed inwards (orbital braking).

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I am Mugs, of the Alien clan of Usa, Nordamerica, a Terran, of Sol.

Mine: "Perception isn't reality. It's merely an abstraction thereof, and quite often not a very good one at that."

Heinlein's: "Staying young requires the unceasing cultivation of the ability to unlearn old falsehoods." "Freedom begins when you tell Ms. Grundy to go fly a kite."