Here's how I see the Glenn and Maggie issues...
Maggie is mad at Glenn because he hasn't exactly been supportive since her incident with the Governor.
Glenn is a little more complicated. (And it's a bit easier if you remember that he's admitted to never being in a serious relationship before.) He just doesn't know how to act. He's full of rage at the Governor, and he understands this emotion. But he doesn't understand how to react to what happened to her. Partially, he blames himself that he couldn't protect her.
Yes, their reactions are irrational. But people don't always act rationally in times of distress. (I think the show would be ridiculous if everyone reacted "perfectly" to every event.)
In real life, you see couples having trouble getting along in circumstances that can't compare to what Glenn and Maggie have to deal with.
Here's how I see the gun issues...
Doesn't anyone on set raise their hand and say, "Umm... How come the survivors rarely ever have ammunition issues or never need to reload? And how come they never miss zombies (even when shooting from a moving pickup on uneven ground) yet can't hit a stationary human?"
I thought I was watching an episode of the A-Team from the 80's. (For those who don't recall... Every episode, hundreds of rounds of ammunition were spent, but NOBODY ever got hit.)