fix paypal issues in magento 1.9

[login to view URL] - Paypal-related issues. Discount issue: We offer 3 types of discounts, a) 5% off the order, b) free shipping and c) a fixed amount like $4 off. These were working fine. Then somewhere down the line, Paypal started putting up a message Try Again if a discount was applied. After some investigation we determined: 1) it does not work at all if a fixed amount is discounted. Paypal tech support told me a discount must be applied to a specific item, not to an order. No explanation as to why this used to work. 2) it works some times when a discount % is given and fails some times. A discount percent is applied to every item on the order, so paypal has no explanation. 3) free shipping seems to work all the time. Shipping issue: We have only a flat shipping based on the cost of the order which maxes out at $8. The customer is not given any shipping choices. Yet they are first taken to paypal where they "choose" shipping, then returned to the site to "choose" again. I would like the entire order completed in paypal before returning to the site (this is how it works on my previous site and just about any other site I have ever visited). If not possible, return to the site with the shipping already chosen or at least already filled in. All these extra steps cause visitors to abandon the cart. After returning to the site and choosing shipping, they have to scroll down to the bottom of the page to complete the order. This is not intuitive, particularly on a cell phone. There should be a message "Click the complete order button on the lower right to finish." Note - a previous developer tried to fix the above. Now in paypal instead of showing the shipping fee as $8, it shows best_table_rate_8 which looks very strange. What is involved in going to magento 2?