1) What's the light source at the start of the adventure? Doppelgangers have Darkvision, so the "doctor" wouldn't need to have a light on.
I think the AP mentions candles. While doppels have darkvision, darkvision doesn't offer the ability to see color, so maybe she has them so she can see blood in vivid detail.
2) Not to overthink it, but how did the PCs and the orderly get in there? Presumably the PCs were brought in before the earthquake closed off easy access, but how'd she wrestle the poor orderly onto that table?
Strength, surprise, maybe. Also, she didn't necessarily do it alone (she could and probably did(?), just saying).
3) If the doctor escapes, her only exit route takes her past the barricade. Presumably the guards would comment on this? "We had one just a minute ago, looked like a little crying child..." Actually, that's useful information, so I wouldn't give it to them without a successful face roll of some sort.
I had her just run on past, and rolled for the guards shooting her. One tagged her, which was good for the PCs, because when she's with another doppelganger, that's a very difficult encounter. But if your PCs are very tough and they don't need such an assist, it's reasonable that she ran past the guards and got into the dark hallway before they could react.
4) I've seen a couple of PBPs where the orderly survives. This can create some complications for good-aligned PCs, as keeping a guy with 1 hp alive until they can cross the barricade isn't easy. (One DM solved this by having the poor orderly grab a blade and cut his own throat rather than face what's up there.) If he does survive, any thoughts on how to stat him up and/or run him?
In my case, Scaen stabbed him, and got him into negatives. He either stabilized himself, or the PCs did it (I don't recall exactly). They healed him (channel) but note that does not automatically wake him. They checked his status, but they did not wake him. They left him there, to return later, and he became a ghoul minutes later. This doesn't answer your question specifically, but I want to illustrate what could happen.
If that didn't transpire, I'd have him provide basic details about the asylum, maybe have him knocked out by falling debris (which could answer question 2), or captured immediately, so that he doesn't know exactly what went on.
EDIT: Regarding his stats, he's a Survivor.