Pruning Halesia diptera trees
I'd like some advice on pruning Halesia diptera. I have four lining my driveway, which vary in height from about 3 - 7 m. All were planted at the same time/same size, but have varying growth rates. One is unfortunately having a problem: the main leader is leaning. At waist-level, the trunk starts to list. The main leader goes off to the left. Two smaller/shorter side branches go off to the right. At this point, the main truck is about 5 cm dia. I can't get a good photo of the top since it's leaning into the neighboring tree. Is there any way to prune this to regain balance?
The other issue with these trees is that new branches often grow near or right at the branch collar (over and under, like tomato plants). Should I continue to cut out the new axillary branches or let it do it's thing?
Finally, what's your favorite book/resource for pruning trees and shrubs?
Thank you for any advice.