PHP/Wordpress Quote Form Customization

Project details have been updated. Please read everything carefully before bidding. I currently have a taxi booking form on my website. It is fully functional but needs to be customized. The form is built in PHP and uses Wordpress. This is what I currently have: The current form allows a user to type an address into the FROM and TO textboxes, then, it allows the user to select the auto-fill suggested address from Google API, and then uses Google API to get total distance between the locations and then calculates the total price based on the price of the taxi per kilometre (price per km per vehicle is set in the WP backend). !!!!!This needs to be customized is the following:!!!!! - I want a list of my own choice of FROM and TO locations (via drop down menu). I should be able to add/remove/edit these choices from the wordpress backend. - If an airport (4 airports total) is selected in either FROM or TO drop down, I will supply fixed flat rate to all other FROM/TO locations. Keep in mind, we will need a different fixed flat rate for 5 vehicles. I should also be able to change these prices anytime. - If both TO and FROM locations are non-airport, we will need to calculate the distance using API between both locations and then use a formula with price per KM ranges to calculate price per different vehicle. Please note the website is already active, and has a fully functioning back end, where I can add/remove/edit vehicles. I have attached a screenshot of the layout of the form that I want.