Customize ultracart Javascript checkout

I am looking for a PHP/Javascript developer to work with long term, this project will be your interview! I need you to rebuild my current ultracart checkout page so it is easy to edit and work with moving forward (the previous developer built it in way that has made it hard to update). You will have the choice of using my existing working code and modifying it seen here: [login to view URL] or starting from the sample code and documentation Ultracart provides here: [login to view URL] It should be a one page checkout with the same design as my current page (I will provide FTP access upon project acceptance). You will need to make a few small updates to the functionality: 1) Add the ability for the admin to show/hide the option to checkout with paypal using a URL variable (Paypal is already integrated with ultracart you just need to surface the feature because it is currently hidden) 2) Paypal set as default payment method for non-US based visitors 3) The ability to pre-populate form fields by passing URL Variables to the checkout page 4) The ability to populate all UC custom fields by passing URL variables to the checkout page BONUS 5) Update the design to make the page responsive If you are comfortable working with new APIs and from existing code this should be a relatively easy project. In your reply please tell me if you have worked with any other shopping carts and if so which ones. Generic bids will not be accepted. If you have questions please include them in your brief. Also please include your monthly rate in your brief. If you complete this project on time and on budget I will hire you full time! thanks, -Bobby