If they like it as it is, and it shows promise, they will be interested.
It would unlikely that a final tweak would make the difference between a yay or or any.
Remember no one is as invested in this piece of writing as you. For your own sake, step back, take a deep breath and understand that the quality of your writing, whether its marketable or not, will already be evident in what you have submitted.
And also understand that it might just not be their cup of tea.
Learning to take rejection calmly will really help. For feedback, join a creative writing group, don't ask those who have rejected an MS to give a detailed feedback.
Its not about you often. Out of the hundred or so MS submitted a week when I was in an agency, I can hand on heart say in two yeas I only found one good submission.
Just so you know the kind of volume, if not quality you are up against. There is no way an agent would be economically viable if they gave in depth reports for every submission.
There are literary consultancies who WILL critique you work for a fee. Check out the reputable ones if you feel this would help you move your book forward.