Yes, you need one block of our View Cart code on every page that has any number of our Add to Cart buttons. That should also solve the problem you described with the go-back link during checkout.
On the product pages I looked at, I noticed you have two separate Add to Cart buttons for each product, one for PayPal buyers and one for everyone else. That's not really necessary, since our cart supports PayPal as a checkout option. Having two separate buttons and carts for PayPal vs. non-PayPal would likely confuse many buyers, who may just get frustrated or leery and leave your site without buying anything. There should be no difference in cost whatsoever for you or for buyers using our cart with the PayPal checkout option vs. using PayPal's own cart buttons.
To add a PayPal checkout option in your E-junkie cart, just go to your E-junkie Seller Admin > Edit Profile and enter your PayPal login email where indicated, then Submit to save changes.