had to google caliper lol

I'm pretty sure you mean Prunus angustifolia because that's the only one I see get called Chickasaw plum but there's also Flatwoods/Hog plum, Prunus umbellata.

I have P. umbellata and it was over 5' 6" feet when i bought it (this is a species that can be sour tho) from this place in Jax http://nativeanduncommonplants.com/

I fertilized it in mid to late summer again with citrus fertilizer and it responded with a second burst of growth about equal to initial spring one so you might be able to experiment with that to get it to grow faster.

Not sure what its diameter size is, sorry. It's certainly thicker than my thumb, though.

Edit: I've never ordered from these people but i have considered it. https://www.wilcoxnursery.com/plants-and-supplies/trees/chickasaw-plum-15-gallon/