I'm a member of MPEG local 700, motion picture editors guild since 1979
The issues are the following: Is there another editor on the job working with you? If so, then you might be relegated to the 1st assistant credit. I must assume that this is not a union feature because they would be in violation of many provisions, so let's go forward from there.
I'll tell you that people are generally warped when it comes to the creative process. From what you are telling us about your involvement with the film, you are functioning as the editor. Not my opinion, just fact based on the description that the MPAA uses to describe what an editor is. This has nothing to do with experience, or any subjective matter. You're working with the director, cutting scenes and building a feature cut. That makes you an editor.
My take is that you deserve the credit only if there is no other contributing editor that has been contracted to edit the feature. No one is going to have the balls to confront the issue past that, as this is common practice to exploit talented individuals at little or no money to get the job done. So, if you do a good job, and lots of people (including yourself), like the end product, and they finish it that way, You should get the credit.
Now one last think. This is how assistant editors get editing jobs. They put together a reel that shows the work that they did. Who else will be more intimate with your cut than you are? I'm a seasoned pro and I couldn't b.s. my way through lying about what take you used for any given scene, but you can. So, if all else fails, you have materials to build your reel so that you can search for work in the future.
Best of luck,