It sounds like you are doing fantastically!! As for single side vs. double side, it really is whatever works for you and your lo. Breasts are all different shapes, sizes, and storage capacities
and babies' tummies are the same way. Some babies do well with single side feeding, others do better taking both sides at each feed. Still others single side for a while, then double side during growth spurts. My ds (from about 3-5mo) used to single side in the morning and early afternoon, but want to double side during the evening cluster feeds. You're doing compressions to ensure that he's getting to that fat-rich hind milk, stirring him, and then offering the second breast. You're even stirring him again to get that EAS pattern started early! My hat's off to you, you are doing GREAT!!
With this "double" feed, he is able to go 2-3 hours from the END of the nursing session. When people talk about about feeding every three hours though, they mean from the start of feed A to the start of feed B being a total of 3 hours, right? So, am I playing with fire doing it this way??
You are right - when timing the space between feeds you use the time at the beginning of each feed. So if feed A begins at 7am and lasts for 45m, and feed B begins at 10am, then your lo has gone 3h between feeds. I would try to wake him at the 3-ish hour mark to feed again - newborns are very sleepy and would just keep sleeping if you let them. I wouldn't say that you're playing with fire, but by waking to feed at 3h intervals during the day you really ensure that he's getting as many calories as possible, and that will hopefully help him sleep for longer stretches at night when he is ready.
HTH, and congratulations on your little guy!