to troubleshoot the view cart button, I would need to see the page in the browser, the view cart button uses a javascript on click behavior to redirect to the cart page, to troubleshoot why it is not working, I can only do that by visiting the page ion the browser.
for the shipping on clear cart, what shipping provider are you using? you could add code to the clear cart behavior to clear the session that contains the shipping quote, but i need to know the provider in order to tell you what session variable that would be.
For the modify button, bind the initial values for the form elements on the checkout page to use the corresponding session variables from the session collection.