I wish I had the definitive answer for you. I can only tell my own story with dealing with this. When I was at my heaviest, I spent two years sleeping every night in a recliner because my reflux was so bad. Once I started losing weight (CW style at that time) my reflux went away. I've had my gall bladder out too, and like you, it didn't make any difference one way or the other with the reflux.
The thing is, reflux actually causes damage. It's like a burn in your esophagus and in your trachea if you're one of the unfortunate who aspirate as well. It has to heal or the least little thing will irritate the injured tissues.
If you're not sleeping with your torso elevated, I highly recommend that as a first step. Propping pillows doesn't work well. It's better for both reflux and spine to use a foam wedge or put blocks under the headboard legs of your bed. The idea is to stop the reflux long enough to let those inflamed tissues settle down and heal.
You've already identified several triggers for yourself. Oranges were one of mine, and the WORST trigger was a combination of sugar and fat in the same meal. Eating large meals-- regardless of quality-- is also a common trigger. The sphincter at the top of the stomach is weaker than it should be, and lets the stomach contents backflow if under pressure.
You may try eating just until the edge is off, then eating lightly again when hunger returns. It's a pain, and not a lifelong thing, but again, the goal here is to heal up so some sort of normality can be, well, the norm again. Even eating perfectly as for content, if the quantity is too much, too close to bedtime-- I'll burn at least a little.
Your stomach may empty slower than "normal," too, so you may want to bump the last meal farther away from your usual bedtime. Lessee.... what else? Alcohol always burns me if consumed in the evening, and while I can now eat sweeter citrus (tangerines), navel oranges and orange juice are like swallowing acid. Tomatoes and tomato sauces don't bother me any more, though they did till I was well-healed.
I know this is a lot of semi-random stuff, but maybe something here will help, I hope!