slug damage aside, I think your plant is doing well. I love pruning plants into standards so I can appreciate your interest in doing so. But keep in mind that some plants, brugs, crape myrtles, just want to have multi trunks so you are constantly cutting suckers, side branches, etc. If you've decided you don't mind putting effort into constant pruning, just take off what you don't want. It will not damage the plant.

I grow all my brugs inground and have given up on the standard look to reduce my work load, I see yours is potted and wondering if you plan to grow it that way permanently. Potted plants may not be as prone to develop side shoots. I don't know. But if that is the case, then your pruning chores will be drastically reduced.

for all the info you could possibly want go to http://www.brugmansia.us they tell you everything about growing brugs and I would ether put it in the ground or in a large pot it will fall over and brake in those cloth pots

I agree with Mickey .................. a brug this large needs to be in a larger, sturdier container if you aren't going to put it in the ground.

Thanks for the advice everyone. This brug is going to have to stay potted for at least this year. I'll let it grow into this pot and then double the size or so. When I got it it was in a very small container probably a bit shy of 1 gallon and completely root bound. The new growth I have is distorted and I am hoping that is because of the small pot it was in at the nursery. Its also been in the 50s and 60s and rainy the past few days so not sure if that has anything to do with it. Can't see any noticeable pests. Here are a few pics of the new growth. As you can see the new leaves are pale, shiny, and curled.

I see at least 2 flower buds on your plant!