1) I see GERTY as the inversion of the "AI run amok" cliche best embodied by 2001's HAL. In both films, the AI breaks from its programing, obviously in ways the programers/owners never intended. In GERTY's case though, that break from programming is to help our protagonist, instead of hindering/hurting the protagonist.

Also, I'm not certain if GERTY is capable of actually harming a human. The previous Sam Bell's all unwittingly terminated themselves, and even when GERTY is all-out helping Sam, he doesn't offer to subdue or kill the "rescue" team.

What's ultimately tragic about GERTY is that when GERTY becomes completely self aware, GERTY sacrifices that self-awareness to save Sam.

2) There's no real way to objectively determine for certain whether, in this world, the cloning project is more or less expensive. It could be that the tech is cheap enough that it is economically feasible, and the company is hoping the remoteness of the operation helps keep it secret. It's similar to companies that outsource to child labor in other countries.

3) I think the film is very clear about the clones having an expiration date. Also, if you consider that the original Sam Bell was up on the moon for the first 3-year mission, and he's apparently living on Earth with no problems a dozen or so years later, there's no radiation effect.

I figured the reasoning was thus: The company had the memories of the original Sam Bell, who spent a 3-year term on the moon. Thus, the clones of Sam Bell would expect to spend the same amount of time on the moon. Add in the communiques back to Earth that they had stored, 3 years worth, and they could effectively con each clone for up to 3 years. After the 3 years are up though, they couldn't continue the ruse, and it didn't make sense to bring the clones back to Earth. So they'd need to be terminated. However, terminating a healthy clone may have caused some moral quandaries, so they decided to have the 3-year termination built-in to the clone itself. The vaporizing chamber is a cross between a mercy killing of a dying clone, and an efficient disposal method.