Wow. that is a high resolution application for an accelerometer. In my experience the accelerometer, gyro, and manometer in my MPU9250 is very noisy. I am using the accelerometer/gyro combination to calculate rocket tilt and g forces on the way up, but I really only need an accurate sample about every 100ms. Even if I go 500ms without a good sample it isn't the end of the world. Sampling at 55hz should be possible on a fast processor Arduino, since the sensor can sample thousands of times a second. I am using the DMP built into the MPU9250 and quaternion filters. It takes about 30 seconds of sampling to get accurate, but then it is super accurate for me.
Depending on your application, you also likely need to calibrate the accelerometer. There are a lot of examples to run and get the off-sets required. I calibrated my manometer for another application and what I did was just write a program to output the x,y,z to the monitor (comma delimited) and then I rotated it around in circles for a minute. I then pasted the x,y,z data into excel and graphed it. it was super obvious when I visualized the data to see how best to calibrate the offsets.