A player at 1400 (which is his online rating, so he'd be even lower rated OTB) needs to do lots of basic tactic puzzles, and play slow games to get used to looking around on every move to avoid blunders. Everything else is secondary. Why are we even talking about openings? Or atheism? Stay on topic, people!
In my defense, I wrote a really long suggestion for how to do tactic puzzles and at least one of the things I think he should be doing while playing long games.
After that I don't mind going off topic, because that's already at least a month or two worth of work, depending if he's working on it every day.
I chose your most recent win and loss (from games that were at least over 30 moves).
Two main issues IMO:
1) You're not committed enough to following the opening principals. I'm sure you know them, but you need to make a bigger effort to follow them.
2) Sometimes you'll see a beginner who plays with only 1 or 2 pieces, then when they're traded off they use another 1 or 2, etc.
Then when they get a little better it's 2 or 3, then 3 or 4.
I get the feeling you're at the tail end of it... you're nearly using all your pieces, but you seem to want to start the fist fighting when just 1 or 2 guys still aren't included in the action.
Sort of the middlegame equivalent of the opening principal of development.
This is the best response here. And and thank you for the treasure trove of articles:
https://www.chess.com/article/view/the-principles-of-the-opening
The right navigation bar goes to tons of stuff.
Thanks so much 
. When I post I really hope I can be useful to someone on their chess journey.
Chess is like any skill... you can read about it for 12 hours a day, and learn a lot of interesting stuff, but if you're not practicing then you probably wont improve at all. The most annoying thing about any skill, IMO, is the tedious hours of practice necessary to improve. If you solve puzzles slowly, and carefully, 1 hour a day for the next month or two, you'll probably notice improvement.
I might even say don't play any games during this time. That way you'll be building new habits.
From what I saw you've got limited attacking skills. When your position is +2 or more, you seem to be doing fine....but its your opponent blundering into those positions. You've got to create threats from way less of an advantage.
For example, you played white against the Silician, and got to play c4 before Nc3, for a +.55 grandmaster-like advantage.
But then your attack was to pair Be3 and Qb3 against black's unsupported b pawn, which should have blocked by an easy Nd7. Your attack then went kaputz two moves later and a heavy advantage to black.
Learn the groundwork for an attack and the marching of pawns, instead of positional moves played just to be positional. Its not something that is particularly easy, but it is necessary. Some people go for the London/Colle/Stonewall because attacks usually are launched fairly quickly against 1400 players. Others like myself go deep into solid openings such as Ruy Lopez, where the groundwork is explained quite a bit.