Hi. I haven't read the other responses yet, but wanted to post quickly after reading one of your questions. The Prevacid SoluTab should not be broken or cut and it shouldn't be chewed...not that that one is a big problem with your little one. The SoluTab is a delayed-release medication and it cannot do it's job if it is split in two. As far as the strongest dose, your doctor is right. The maximum dose for anyone under 30kg (66.13 lbs) is 15mg. And Prevacid is generally the go to medication when other things haven't worked.
I'm not saying do not look for another pediatrician, because I don't know your history with this one, and I know how hard it was for me to find a pediatrician that my children were comfortable with and I liked when we first moved to the Dallas/Ft. Worth area. The first pediatrician I found actually called the children by number instead of name!! I'm the first person to say if you are not comfortable with a specific doctor then it is time to start looking for a new one. Trust your instincts. I'm not sure what area you live in, but my children (ages 2, 7, and 9)
In the meantime, there are some things you can do to help:
The first thing is to make sure she is upright during feedings and for at least 30 to 45 minutes afterward.
Check her car seat when she's sitting in it. Does she end up looking like she's sort of hunched over? This can put added pressure on her tummy and make symptoms worse.
When she is sleeping, on her back as recommended, make sure she's elevated about 30%. You can do this safely with a wedge of foam (available at any Hobby Lobby) that is placed under her crib mattress. (It's not recommended at her age to put a pillow in the crib with her because of risk of SIDs.)
If it is possible, try using one of those carriers that help you carry your baby close to your body. They're like backpacks, but not. You can get one that lets you carry her close to your chest, and this will help reduce crying and crying makes reflux symptoms worse.
Avoid tight clothing on baby. It can put pressure on the lower esophageal sphincter which also makes reflux symptoms worse.
You're already thickening her formula with cereal, which is a good thing, but try giving her smaller meals throughout the day and burping frequently (like after every ounce) during feedings. Also, try not to feed her directly before bedtime.
As much as we mommy's may cringe at the idea, giving her a pacifier may help with reflux symptoms. When a baby sucks on a pacifier, it increases saliva production. Saliva is an alkaline and it can help neutralize some of the acid that may come up.
When she's really tense, or after feedings while she is still being kept upright, or right before bedtime, you can try infant massage. It may help relax her, which will help with digestion after feedings and will help her fall asleep easier at bedtime.
I do hope this helps! Please let us know how it goes.