If its your only one, and you think it's stressed because of the erratic flowering, why not leave it, and try to get fruit set for some seeds for next year? And if you want some this year to enjoy, get a new one like you said. But don't rip out the wack one just because you get a new one, if you do that.

I have no idea why that would happen in the first place, however.

Sounds to me like the growth point terminated with the flower cluster. This happens occasionally to my plants too, and I've never been able to figure out why it happens, either. It happened to one of my "Supersteak" tomato this season

That said, your plant will be okay, methinks. In my experience, when the main stem stops like that, a sucker or two takes over in place of the main growth point.

It is called "stunting". The plant itself is stunted and sets its terminals blooms. Stunting can be caused by several different stress factors but the most common is early exposure to overly cold air and/or soil temps. It is one good reason to avoid overly early planting out.

Dave