So if you want to know if your edits are improving your book, consider all these points. It doesn't matter how many times you check for typos if you don't have an active plot or your main character doesn't have an arc. The book should feel TIGHTER with each edit.
Here's some tough love: It's very rare that your 1st book is the one that will get an agent or a sale. For most pro writers I know (NOT ALL; DON'T @ ME), our 1st book is great practice that is ultimately trunked. Start writing book 2 while you query. Forward momentum!
How do you know when it's time to trunk your 1st book? * When you honestly can't think of a single way to improve it further * When you've got 60+ rejections and are out of agents to query * When you're sick of it and have a new story idea WRITE THE NEXT BOOK and query again.
The painful truth is that if your goal is to be traditionally published, you can't cling to 1 book forever. You can't write 7 books in the series and expect someone to buy them. You've got to write 1 great book, query it, repeat-- until you get an agent/sale. Period.
And as I say with every one of these writing advice threads: This is all based on my experience in the world of traditional publishing. YMMV. You may disagree. Every journey is different. There are outliers. You do you. May the odds be ever in your favor.