I looked at the openings in 2 of your wins and 2 of your losses... I think you're doing fine in the opening. You say you want to shift your focus to studying middlegames and endgames, I say go for it.
The important thing is you're not losing in the opening. You're also developing your pieces, castling, and keeping a pawn presence in the center. That's plenty for now.
As for people who say don't study it until 1500 or 1800 or whatever, that's always silly. Every level of player will benefit from being well rounded. That means having some opening knowledge too.
How should low-rated players like me (~1300) approach the opening? There seems to be a bit of a divided opinion on this. On one hand, it seems like the best approach would be to focus one opening and study it thoroughly and get really good at it. Another approach is that you shouldn't be studying openings at all until you're much stronger -- but how much stronger seems to be kinda fuzzy, 1500? 1800?
I played the Italian game for a long time, and I went through a period where I played random first moves, to a period where I cyclically played different major openings (Ruy Lopez, Caro-Kann, Sicilian, etc.) on different days. However, I love with the King's Gambit as a response to 1...e5 -- I really enjoy the chaos it brings and while there's some theory, there's a lot of room for the imagination. I enjoy the Traxler Counterattack. I enjoy big pawn centers and tend to get crushed when I play hypermodernly. Games with bizarre pawn structures on both sides also really appeal to me but I'm not sure which openings to play to get those.
The main question is whether I should play openings that are unsound at a higher level (Latvian Gambit, Schliemann Defense, Dutch Defense, Nimzowitsch Sicilian, etc.) or is it more effective to learn the mainlines even if they don't really fit my strengths and lead to (what I consider) boring games? I am looking to improve and become better rounded and I don't want my positional/strategic sense to suffer. Should I approach the opening different as black than as white? Are random moves and experimentation in the opening the way to go, at least for now? If so, how should that "randomness" be structured? Should I even be thinking about the opening at all?
I want to shift my focus to studying middlegames and endgames but the opening keeps nagging me.