It's good that your app has some traction. I have a classifieds ad site too (targeting Canadian market). Initially I was wondering if I should use WordPress or created it using MVC I picked the MVC approach. The thing is when doing the MVC you have to implement most of the functionality yourself (or your dev) which is time consuming.
In hindsight I think I should've used WordPress and then bought some plugins to add to the missing functionality.

I'd say do the incremental improvement approach because the things you listed would take time & cost a lot.
By 7.9M do you mean 7.9MB ? The app can be 50MB in size but what is important is what the HTML it is generating.

About the monetization you can do some contextual ads and some affiliate links.
You have to be specific when talking to your dev what you mean by analytics. Say when a user does this I want this and that to happen. You can list some scenarios and how the reports should look like.

Good luck!
Slavi Marinov,
Orbisius