I can only give my personal experiences rather than advice, I'm sure someone with more knowledge than me will be along soon.
Professional editing and proofreading can get very expensive, you want to make sure your ms is as close to the way you want it before you embark on that process. If you engage an editor and then rewrite, you may then be paying for the editing a second time once you finish your rewrites. For me being dyslexic any rewrites will need work by a professional.
For my first book my editor, gave me general feedback, which triggered a lot of rewriting, some chapters only a few lines of original text remained. Then the whole ms was put on one side and left for 3-4 months while I worked on something else. The self edit that came afterwards I was then able to do with fresh eyes and not read what I thought was there.
Re beta readers, I find them useful, be that friends or strangers. Be prepared for some feedback to be useful, and some to be an overall critique. My sister is particularly useful for my process as she doesn't hold back. One project at first draft stage she stopped reading at chapter six of fourteen, but her reason for doing so was incredibly valuable for me and when I go back to that project there is a few months of rewrites just from her three lines of feedback.
The disadvantage to having friends review your ms is they may be kind to you and not be as helpful as you require. The flip side of the coin using strangers is you don't know what use their feedback is other than a subjective point of view.
Have you looked at the one to one sessions available here, maybe speaking with an agent or book doctor would be a place for you to work out your next move?
Your blub sounds interesting, having just been working on one myself I can see some room to make it more concise and hook the reader slightly more, but the premise is one that sounds like it would be a good story.