I'm not in Finance, but I can write a few things about GMAT.
First, I don't think scores from practice tests are reliable. I never got a score from a pratice test that was close to my actual scores. Even the one I did on the day before the actual test was really wrong. For some people actual scores are higher, for other people they are lower, for other people they are right. So, I don't think you should make big plans before you know the actual score.
Second, I think someone with your background should be able to get 50/51. I guess you know all the Math that is needed, then it's just a matter of using a good strategy.
Third, I often recommend people to take both the GMAT and GRE. Some people do better at GMAT, some people do better at GRE, but it's hard to know. You can take both, and use the one that makes you look better.