I'm not an expert in grammar, but since I have so many, many lovely grammar books, I think I might be able to help.

The first case:

Nowadays both sentences are correct. With items in a series the final comma is often omitted, especially where this wouldn't result in ambiguity (even though William Strunk wouldn't agree).

The second one:

The correct one is: "Hi, how are you?" he asked. That's because tags are always part of the same sentence as the dialogue (even when you have ! and?).

The third one:

In majority of books that I read the similar examples would treat dialogue as an inserted sentence (sorry I can't remember how it's called in English), so it would be:

My heart gave a wild lurch, I exclaimed, "Holey crap," and jumped back my heart now racing.

But when I wrote sentence like that my beta would always rearranged it different (and I always forget to ask why) and I can't find any grammar rule that would apply for this kind of situation, so I'm lost about this one. Sorry.

Hope somebody else would know about this. I would like to hear which one is correct and why, too.