Gimli was part of an army at Helm's deep, not a party of 15: I don't think he took on all those orcs
at once. But yeah, it is unrealistic. PJ should have just stuck with the book version of the escape from Goblin town, which makes sense and which also would have saved him the silliness of Bilbo watching the dwarves run by and doing nothing because, apparently, he didn't think they could handle Gollum.
As for PJ getting more serious in the future, I wouldn't hold my breath.