Hey there!
So sorry to hear that you've had so many GI issues with you lo! That has to be tough! Reviewing your routine - it looks really great, she's napping great, sleeping almost a 12 hr stretch at night, minus the wakings to eat. If I woke up in your shoes tomorrow, I'd probably not change a thing, and that includes, continuing to feed at night, AT LEAST until she has her GI appt. That way you can get a better grasp as to what is going on GI wise, and if there is really a problem they want to investigate further.
She is also getting right at 5hrs of naps during the day, and that seems to be a good bit - it isn't inappropriate, as she may just be a baby who needs her sleep more than most. The only thought I have re: these naps, is that it might make her a bit less tired for that night time sleep, and thus make her more likely to wake if she is a bit hungry. Her weight seems good, compared to my dd - she was right at 13.5lbs at 4mo (8lb at birth), and a 5-6oz bottle was also about what dd was doing at that age.
So, again, I'd probably continue to feed in the night at least until you see the GI doc, and see what they say - you may even ask them about the night feed and see what they say. If you do decide to wean the night feeding, I would do it gradually. When we weaned the DF, I dropped the # of oz by 1oz, and brought the feed 30min, or an hour (whichever you like) earlier every 3 nights. So if you decided to go that route, it could look a bit like this:
Night #1-3 -Wake her at 2:30, and feed 3oz (so to interrupt this 3am waking, and keep it from becoming a nightly habit-I wouldn't actually WAKE her, I'd do it like you do the DF)
Night #4-6-Wake her at 2, and feed 2oz
Night #7-10-Wake her at 1:30, and feed 1oz
Night #11 - do pu/pd if she wakes and cries
That's how I would try to drop it if I had to, but others have done it differently. I always liked the gradual approach, because then it can give her a chance to work those calories into her daytime calories without a drastic drop in calories that she suddenly has to compensate for during the day, that her tummy can't handle all at once.
Hope that makes sense, I know others will be along to offer their thoughts too! Good luck with the GI doc!!