I’m sorry no one answered your post..  Let me try.  First, the ugly bumps are Apple Crown Gall; here’s some info: 

https://www.ndsu.edu/agricultu.....nd%20woody.

Some of the above sites info: 

“Agrobacterium tumefaciens

Symptoms

• Crown gall is caused by a soil-borne bacterium that enters tree wounds caused by mower damage, pruning, frost cracks, insects or planting damage.
• The bacteria stimulate the tree to produce plant hormones that cause a tumor or gall to form.
• The galls most commonly occur on the roots or on the trunk near the soil line.
• At first, the galls appear light-colored and spongy.
• As the galls mature, they turn dark brown and woody.
•   Management and other important facts

• No cure exists for the disease, and it may kill a young apple tree by girdling the stem.
• A mature apple tree may be able to tolerate crown gall.
• Carefully inspect apple trees to avoid purchasing a tree infected with crown gall.
• If a recently planted tree develops crown gall, remove the tree and adjacent soil; the bacteria can persist for several years in the soil.
• If your property has a history of crown gall infections, avoid planting fruit trees or other susceptible plants.  Author: Esther McGinnis”

I’ve had more established trees survive, if not thrive with his disease.  Worst part, it can spread to other apple trees through pruning, or sharing infected shoots for grafting..  Sadly, I suggest digging yours out and removing it.  

Otherwise, it’s trained as an Espaliered apple tree.  Meant to have a trellis or supports, it will not make a stable free standing tree.  If it were not diseased, it might be worth the time and effort to severely prune, or provide custom support.  

‘Right now,’ it may look relatively healthy and be in ‘full leaf.’  But every season it’s allowed to remain, a healthy replacement could be growing into a solid stand alone tree