Questions about Hubble's brand new view of an interstellar comet (video)
TL;DR version, Yes, yes, distortion. In more detail:


HST's orbit is approx. 90 minutes so this will cause the breaks. Some more information is given in the Orbital Constraints section of the Cycle 27 guide for proposers.
Since HST is having to move to track the moving comet to keep it in the (small) field of view of the instruments, it will likely need to roll the spacecraft. This is to keep suitable guide stars in the Fine Guidance Sensors, to keep the Sun on the solar panels for power and to keep the pointing constraints of not looking to close to the Sun, Moon or Earth satisfied. These are discussed in more detail in the Orientation and Roll constraints section of the primer/guide for proposers mentioned earlier.
This is due to the geometric distortion of the optics in UV/Visible (UVIS) channel of the WFC3 instrument as described in more detail in this section of the WFC3 Instrument Handbook,