Where exactly is the numbness in the arm?
It's on the inside (closest to body) above elbow and sometimes can feel it on the inside of my wrist like to pointer and index fingers.
Numbness in a specific area of the arm, and the hand - as you describe - does seem to be related to a nerve issue.
When nerves become slightly irritated, they can cause numbness, or tingling. More severe irritation can cause pain in the same areas.
There are different nerves which travel in the arm, and they do go to different parts of the hand, so the fact that only some of your fingers seem to be involved makes it sound like a nerve issue. (A circulation issue, for example, would be rare, but also affect the whole hand).
So a nerve conduction test may help to look for issues such as carpal tunnel or ulnar neuropathy which can cause numbness. Another potential area to look into would be issues with nerve compression in the neck, which can cause similar symptoms down the arm as well.
That insight helps with the arm numbness, but could that also cause face, leg numbness and coldness of the lower ab? The arm is the most pronounced, but I do think I feel a little numbness at the other areas I mentioned.
No, issues in the arm should not be related to the face nor the leg.
However, if all of this is related, it could be from an issue from within the brain, as an issue with the right side of the brain can cause symptoms (in your case, numbness) on the left side of the body.
However, if that were the case, it generally would affect your whole left arm, not just the specific area you describe.
What are possible issues that could cause this? Is it just too broad to tell with out testing?