How split is too split to save a tree?

How split is too split to save a tree?

I've got a couple of companies coming next week to tell me what they can or can't do, but I wondered if anyone here had an expertish opinion? Live oaks are not made for frolicking in the snow.
Blue & Pink

Blue & Pink

Wiegala? Dying?

Wiegala? Dying?

Tomato Hornworm & Mystery Plant

Tomato Hornworm & Mystery Plant

Plants for a shady area of my yard

Plants for a shady area of my yard

Is this phlox?

Is this phlox?

Square Foot Garden

Square Foot Garden