I think you are lucky to live in a municipality that appears happy to let you do as you please without engineering drawings, licensed contractors, insurance and permits...

Bury the whole pipe, it's being pumped uphill anyway, so go under the sidewalk and to the curb.
Even if it creates a low spot in the 2" piping - so what? That trapped water will just sit there static when pump is not running.
Cut the sidewalk open to bury the pipe, drill or cut through the curb and terminate the 2" discharge in the curb face.
The cost of this will not be high to get that last stretch.
A small PVC back flow preventer will not clog easily especially if you 45 the curb discharge in the direction of flow.
You can place the back flow below the grass between sidewalk and curb where it can be accessed for service.
You can even put a 45-T junction on the discharge side at the backflow so you can open it and flush debris out of it.
Once you have the above scope done, and it has run for a month or two, evaluate what works and what doesn't..

Everything should be accessed for easy service or replacement, which brings me to my next, larger point:

This is a battle between nature and technology. Which one of those two relies on engineering, construction and maintenance?

The burden is on your technology.
You *are* making it as simple as possible, but for sure some part of this will eventually fail and need maintenance.
Just anticipate it and make it easy to access or improve as needed.

Then consider how much maintenance your neighbor who filled his property has had to follow up with.. What is the comparative cost of filling in Lake Kevin?

Long term - do you think you will dry out the black clay?
Because drying clay will shrink and introduce more slope to adjacent properties, which will attract more runoff water.. the ripple effect will possibly need another solution.. beware of nature - she is a b!t$$h
- Art