It's perfect again, and I'm anxious to submit it. Where do I go from here?
Hire a professional editor such as BookMakers. Whether or not you are going with an indie publisher, a self-publisher, or a traditional publisher, your manuscript needs to be professionally edited FIRST. Most of the publishers, whether indie, self or traditional, have editing staffs. However, because of cut-backs most editing staffs, even at traditional publishers, are small and rely upon "mechanical" or "electronic" editing, especially for mid-list and first time authors. A software program is not going to help you work the kinks out of your book and will not help you locate fatal flaws. You need people for this - trained, experienced people. A professional editor will work with you on content edits first. Of course, they'll identify basic sentence level errors that jump out and need to be corrected. But during the first rounds of editing, the emphasis is upon the clarity and flow of the content.
Did you say "the first rounds of editing?"
Yes. Start rewriting and making the changes until it's perfect again!
Then send it back to the editor. If the editor feels that your manuscript is ready, it will receive a final proofreading and copy edit. The best editing companies will use two people at the final stage of proofing to catch anything the first editor has missed. If the editors think the manuscript still needs work, they will discuss those possible changes with you. If you choose to make the changes, the previous steps are repeated. Make the changes. This process continues as long as suggestions to strengthen the manuscript can be made and until you are completely satisfied with the manuscript. Once your manuscript is all that you ever dreamed it would be, you're ready for publication.