Judging from this question and another question you have posted, I can see you are having some trouble with 「で」. 「で」roughly functions like "with" semantically and syntactically in these expressions. Sometimes "with" alone doesn't quite cut it, but with a few more words, can render this expression in English.

「じゃあ、そういうことで」:With that (said/settled), let's call it a day.

Similarly in your quoted line, 「ってことで」also concludes the conversation or settles that slice of an exchange. More or less something like this:

> [My dream]
>
> 遊: civil servant or full-time employee at a good company
>
> 理々: That's not a dream! It's just a stable plan.
>
> 遊: Okay, my dream is stability then!