I don't an experience asking references that were not professors but did have trouble. It felt awkward to even ask because I didn't feel like there was a strong connection with many professors. I graduated this year but am having trouble finding a third reference. Some school only require two and I haven't seen any that need more that three, it sounds like you have that. I may have also read that references should just be associated with the field, not just professors. In case the gallery owner and the film employer would be fine.