GERD vs. NERD vs. LPR vs. Gastritis vs. Esophagitis... whew! It can be so, so confusing and frustrating. We all feel you on that one.
As for the exercise, I have the same problem as my Yoga classes are from 1830-2000 and I usually go to bed at around 10... it's tough. I usually try to eat something at about 1730 and then just hit the sack a little earlier on those days, which doesn't always work - sometimes I just have to stay up until midnight. I know this isn't feasible for everyone, so unfortunately you might just have to work it out through trial and error. Be careful that your tummy doesn't get too empty, though... once my stomach was hurting so I didn't eat for about 8 hours and I ended up in the ER with terrible, terrible stomach cramps.
I'm sorry you're suffering. I've also been researching Nexium and effects and found the same studies that say we may have too little acid production, etc etc. Without a degree in medicine, I think certain aspects of this disease might always be a mystery to us. It might be a good question to ask your PCP or GI doc.
In the meantime, I hope your symptoms subside and that you get some relief soon.