You could make an argument for any of these options based on this passage, I think, provided that you allow for a sufficient degree of nuance.

Ripley's life depends on his ability to act spontaneously, in response to changing events around him and the shifting of other people's views. In order to try to curry favor with the people he is targeting, it is necessary for him to be able to alter his behavior, as we see here. He himself is happy to pursue any of these options depending on how he thinks each will be received.

In the same way, then, Ripley is sensitive to the opinions of others, but not because he personally needs other people to like or approve of him. Rather, he has to consider how other people will think of him and his behavior because this will impact his social status and how easy it is for him to conduct his criminal behavior.

Meanwhile, social convention is something which Ripley flouts through his criminal behavior—but it is equally something he must be aware of in order to remain undetected. So, while he is indifferent to it on his own terms and as regards his own behavior, he is not indifferent to it in the wider scheme of things. He is very aware that it exists and that he must work with it, not against it, in order to prosper.