Create custom widget for Divi Theme Wordpress site with API Integrations

I'm looking for a smart, talented and enthusiastic web designer + developer who enjoys a challenge and has the skills, experience and confidence to propose solutions, not just take instructions. I am not a developer or a designer but I know what I need for my customers. I have a detailed mockup of a solution I need to build to replace the shopping cart on my existing wordpress Divi Theme website. The mockup was created in Google Slides, it's not perfect but it's pretty clear. The three outcomes I need are: 1. A widget that slides in from the side of the screen and guides new and existing customers through a step by step process of placing an order for my 3D modeling services. This same widget will fill the whole screen on a mobile device so the experience of using it on mobile or desktop will be identical. The widget will have an in-built calculator. Users will input a dollar value into the calculator, answer some questions and select from a number of product add-ons. The calculator will use this dollar value along with their answers to the questions and the add-ons selected to calculate a price. They will then be able to save the quotation for a future time or pay at the checkout. the checkout must have three options Paypal, Credit Card (Stripe) and Bank Transfer. 2. A User Accounts area, where my customers can login at any time and view the details of all their orders past, present and pending in the one place. From this area, my customers must also be able to select and purchase add-ons for existing orders with ease or retrieve quotations they had created using the widget in the past. 3. API integration. There are a number of integrations I need that will most likely use Zapier and connect my shopping cart with MailChimp, Dapulse (our project management software), Paypal, Stripe, Gmail and possibly Dropbox. Think you've got what it takes? PLEASE NOTE: This project should not be regarded as an opportunity for gaining new experiences and learning new skills "on the job". I am genuinely interested in working with someone who represents value for money - you need to know what you're doing, make a plan and get this done efficiently.