Experienced gardeners please help Katsura tree pruning / care advice?

NW, USDA Zone 8, Full sun. 2 katsura trees are planted in planting strip in front of my house and have been getting vandalized. I've been waiting for them to grow taller before limbing them up, but now I think I might need to start now due to the vandalism. The vandal is indescriminately breaking branches whether they are in the way or not, so pruning probably won't stop them. I will do some repair pruning, but I wonder if I should hold off limbing it up. They have been in the ground for 4 years now and have a single trunk. I'm also wondering about water. They have been growing moderately, and I still give them supplemental watering in the summer due to the fact that they lose their leaves prematurely in the late summer. I know they should be on their own as far as watering is concerned, but I've been babying them anyway. The soil has been amended well with compost and mulch but it still gets very dry, and a lot of drought tolerant plants surrounding. What to do about vandals?