Wanted to give an update.
After 4 EMG tests the FPL muscle was finally tested properly and had signs of fibrillation.
After 6 months of no improvement at all I was about to get a surgery for the AIN syndrome (the medial literature recommends waiting 3 months before surgery). But than I suddenly saw a small improvement,, so the surgery was canceled in the new few months my thumb improved and healed.
As for the MACN nerve injury (the sensory nerve) - it improved over the next ~6 months too. (as the Tinel signal advanced along the arm).

So that is how that story concluded. For almost two years everything was fine. But two weeks ago I felt a similar sensation along my forearm.... the right arm this time. Over the next two weeks it got worse, sharp burning pain when I stretch my arm, burning sensation on the skin. Tinel signal at about the elbow. This time it seems that the LACN nerve has a lesion.

I went to a good Neurologist, and he pretty quick he brought up the diagnosis of recurring Neuralgic Amyotrophy, and recommended to check for the hereditary form of it. (but I don't have family history of it). He also did an EMG test, which revealed traces of some axonal damage in more muscles innervated by the brachial plexus in both arms.

From what I read online, the idiopathic form is more common than the hereditary form, but in most cases of the idiopathic form it doesn't recure. (but in some cases it does).

What caught my eyes was this sentence in the article "The neuralgic amyotrophy consultation" (I can't post links):
"Sometimes the only signs of an attack are annoying pain in the upper arm lasting a few hours with a subsequent loss of pinch grip for a few months, caused by a lesion of the anterior interosseus nerve."
Which is almost exactly what happened to me two years ago (my pain was in the forearm).
And also those sentences:
"NA can also present with pain and sensory symptoms only, frequently in the distribution of the lateral cutaneous antebrachial nerve"
"Any part of the brachial plexus, and clinically any muscle or skin area can be involved, in all sorts of combinations. Sensory symptoms or pain tend not to correlate with the localisation of the paresis."
Anyway after reading that article it seems that the diagnosis is spot on. The article describes everything that I had.

But I am not sure if this is another attack of it, because I didn't have that pain again, or is it still part of the previous attack or something like that?

So that is it for this update.