Good to see others looking into tree model viz. I've done work with larger scale tree visualizations and found you quickly run out of space. I wound up using interactivity to reveal branch level info, dynamically pruned the tree based on train support, and I used a more sophisticated layout technique to pack more info in. https://www.google.com/amp/s/blog.bigml.com/2012/01/23/beaut...

FWIW visualizing trees like that helps spot problems really quickly. Overfitting behavior typically involves overusing a certain field, or growing long and relatively narrow branches.