Think in terms of templates
Chances are, you don't have 90 totally unique pages (if you do, you probably have another problem on your hands) For most apps (or sites) you have a handful of templates that are capable of setting up the central elements of the interface.
Start with the views
You've put a ton of work into creating these 90 views, so you probably know the templates quite well. Go back and identify the 6–12 key views that answer the critical concerns about UI structure (that seems to be the sweet spot in my experience). You're looking for the ones that can act as UI standards for everything else.
Then evaluate the devices
There's a lot of devices out there, but they aren't all that different. Since you went out of the gate with iOS7 and an iPhone 5, I assume that's the bulk of your target audience. That should layout out your iOS strategy pretty clearly. Are you really going to see a lot of users on iPhone 3s? Unlikely. You could indicate what the reduced screen real estate does on a couple of key views and leave it at that.
Now you have to ask yourself if you'll do a fully native Android UI skin? Does your current design look very iOS? If so, you might want to sprinkle in a little Material Design, account for the handy persistent back button, and layout those key screens again. Not 90, just the handful you identified in that last step.
Finally, you have to consider tablets and the dreaded phablet (stupid Galaxy Note!). Are you going to accommodate them too? At the very least, it's a good idea to do a couple of views for tablet. If it's a big use case, do all of your main template pages for each OS.
Management reality check
Now, you go back to The Management and show them all this awesome work.
"Check it out, guys. I've thought of everything."
You point out that you've solved everything for the primary target device. In addition, you've gone back and addressed every other major device context. From this foundation, the engineers can develop the MVP and test it on everything under the sun. You'll be nimble from here on out and address specific challenges as they arise. It's all good, I've thought of everything.
Use Sketch. You'll be happier.