I'm fairly sure I have beaten that level with three stars, so I will have a few attempts within the next 24 hours and pass on some tips for you. That's assuming I can still beat it with three stars, of course.
I just tried the level for myself. I selected a companion (it makes no difference which one you choose) and did NOT buy any extra moves, nor did I use any boosters throughout the level. The key to a higher score is to complete the level with more moves remaining. The more moves remaining, the bigger the bonus. I simply tried to match the cropsies required to activate my companion and ideally to match them on the grassed areas. On my first attempt, I completed the level with a score of 132,000 and two stars. So with a bit of practice, I'm sure I could finish the level with three stars by using the tips I just provided.