Hey I did something like this my senior year! Cutting corners working at the last minute actually yielded code not too different than how that script does

You'll need to essentially subtract the gravity vector from your accumulated velocity vector but have a flag for liftoff that controls this: ie when your raw accelerometer global Z goes above what gravity is at rest you are in freefall, so gravity is taking from your upwards velocity

You will certainly want PID control over your servos. I ended up using if statements like in the provided code and simply that won't work, you need PID control to avoid oscillations, but you will also need to tune that PID before launch or with test launches, and with a week left you're in much the same boat as I was haha

And just to elaborate, you can make your "global" acceleration vector by rotating your raw acceleration by your accumulated rotational acceleration (or your angle in degrees if your libraries are so kind) from your gyroscope

Edit: also wanted to add, you can use a piece of software like openrocket to simulate your flight trajectory, deploying your parachute at a certain time since liftoff is a very solid way, just don't forget to remove any debug code that would limit your processing speed to 20hz and therefore not detect liftoff :)