Sara, you will do fine in the crit. OTF, OTB or in the pack is a good result. You need the 20 second jumps to prepare you for the surges in the race. In reality, nothing prepares one for racing but racing.
Also, note in the warmup I posted from the track that we do 15 Km of constant speed before doing another 5 km at race pace behind the motor. Then we start efforts such as jumps and accelerations. If you ride easy even if it is for a long time and then try to do a jump, it is going to be hard and feel like crap.