Welcome to NeuroTalk.

A level of 140 is very low.
It will take some time to get you back up to snuff.

Here is a B12 thread. Studies have shown that oral works.
The medical link on that thread discusses it. When you have no intrinsic factor, you can absorb passively when the B12 is in large amounts. This happens in the small intestine, not the stomach.
I'd take 5mg orally daily on an empty stomach and in about 3 months you should be over 400. (Ideally over 1000)

http://neurotalk.psychcentral.com/thread85103.html

The B12 from an injection only lasts 3 days in the blood stream. There is an active transport system in the spinal cord to deliver B12 to the brain and cord. It is dependent on high amounts in the blood and this system will not work as well when the blood levels fall. Some doctors will give injections daily, until blood levels increase. But not all doctors understand this. That is why oral every day, is more natural.

Depending on how long you were low, will determine how long it will take to recover. If you were low for YEARS? It will take longer than if you are only recently low. The neurological symptoms typically take longer to resolve.

And yes do the methylcobalamin since that is the active form.
Cyano is not natural, and your body has to do 4 chemical steps to activate it to methyl. Sometimes that fails.