Before chapter 80 comes out

Just a few thoughts.

Ed's life won't be shortened by using his own energy to heal his wounds. My speculation is, he may even have mastered retanjitsu unknowingly. Rentanjitsu uses existing energy flow, and that's exactly what Ed did.

About May Chang's role...
Mostly comical, she's like a mascot character. However, besides holding the key of rentanjitsu and uncovering the counter attack transmutation circle, I think her biggest role is to show that Scar is not a bad guy. But I do agree she is too much of a convenient character. Chances of her pairing up with Al at the end is high. Ed and Winry getting together is pretty standard.

I've already shared the following thought with Sora about May. In the beginning, May had totally fallen for Ed although it was an idealized fantasy. To avoid a triangle of Ed, Winry, and May, Arakawa seemed to have deliberately destroyed the first meeting of Ed and May. In chapter 47, after Winry failed to pull the trigger, broke down and cried, Ed put his red coat over her. To me, that action felt very out of character. Then I realized it wasn't to show kindness to Winry, but to remove one of Ed's trade mark! Later when the brothers almost captured Scar, May showed up, saw Ed, but didn't recognize him. It all makes sense.