Firstly I find it hard to believe that your dad's truck is burning three quarts of oil per oil change, I guess is what you were talking about and his plugs are clean. Second usually cylinders 1 and 7 are the ones to watch for. If either of those plugs have a lot of carbon on them you have an afm issue. Your plugs look fine to me. Burning a half quart of oil for a 5.3 is normal in my opinion. I don't think any truck I've owned that had the 5.3 didn't burn any oil. Most all cars and trucks on the road burn a slight amount of oil because of the pcv valve system or crank case ventilation. If you had an oil catch can you'd see what I was talking about. On the lifter tick issue, I bought my 2011 5.3 with 73k on it. When I first bought the truck it ticked super loud when engine was cold until it was warmed up. Then it ticked only upon idle. I switched to synthetic oil and the cold tick disappeared completely but the warm tick was still there. Which bothered me. Long story short dealer replaced my lifters. They said my tick wasn't terrible. They changed them to make me happy. After them changing the lifters I continued to run valvoline full synthetic oil. After a few thousand miles you could hear a slight tick at warm idle but not like before. I switched to Mobil 1 full synthetic noise is gone. I've never had any oil burning issues either. Only the crap my catch can catches. When I changed my plugs they all looked normal. My personal opinion is if you have the warm tick your fine. If you have the cold start up tick and the warm might be something to look at. Also if your going to do the lifters get rid of afm all together. If mine wasn't done under warranty that's what I would have done. They also told me the cam showed no signs of wear.