Gambits have never been advantageous for White if Black knows how to defend. This stands to reason...if a gambit really worked statistically and had no counter, it would be played by almost every GM, in every tournament, until it got refuted ...
that's the FAULT in all of your PREMISES. you're ASSUMING everyone is making OPTIMUM moves and that that pawn ACTUALLY MEANS SOMETHING. it doesn't. if i'm going into a pawn endgame, i will lose EVERY TIME! i couldn't get them even with THREE books! i only understood them with the FICS lesson that ISN'T on demand and that i'd FORGOTTEN already a couple months later when one actually came up. the pawn is initiative, i'm an attacker... ANYTHING (like best moves theory... duh!) that gets me into a position where i have an extra piece to throw at a king is EVERYTHING. it's what i need for my style of play.
in the REAL WORLD, where my theory exists, players make mistakes, often over and over again, and my book gives me directions to an advantage that's PERFORMANCE BASED... the MOST LEGIT metric and i don't care who has a reactionary afraid of progress problem with it. theory that HUNTS 1600-2000 scalps is just what this 1440 needs. i guarantee you too... once i FINALLY get booking, that rating will go up. i think i can EASILY get to 1700 in under a year. i've already claimed a FEW +1700 scalps just winging it when i'm NOT tripping all over myself in the opening.
The best way to stay mired in your rating range is to play gambits exclusively and rely on the other player's lack of knowledge. Specializing in one or two gambits, like the BDG, etc. might work great in blitz, but it's a horrible way to improve your chess. You did say you want to get to 1700. If you cannot win pawn endgames as you stated, then 1700 will be a hard road to travel, but not impossible. 2000-2200 would be utterly impossible.
Try these:
When players say they have a "style" sub-2000, what they really mean is they have burned-in weaknesses they can't get past 
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I like the Danish, but I harbor no illusions. Same when I play the Bird which isn't even a gambit...but I am knowingly giving up my advantage in playing white. If you understand you are playing something flawed or sub-optimal but find it fun anyway, go for it. Just don't expect a big ratings jump thereby.
There are some gambits that GMs actually do play quite often. The Benko would be one. Another would be the marshall gambit out of the Ruy Lopez. I believe the latter would have been played in the recent world championship match if Nepo would have allowed it. Nigel Short and Boris Spassky used to play the Kings gambit a lot. I think both played it with the intention of gaining an opening advantage. Kasparov also played gambit lines. I seem to recall he played the Evans gambit on occasion. There are probably others that are worth playing on occasion as a surprise weapon but if you are going to use those regularly, the only way to reasonably expect to get an opening advantage is to play a bunch of different ones, which isn't what I'm seeing happening in the forum threads.
Yeah, you see the Benko all the time, I mean there's Caruana vs. Aro....oops, nope. Well there's Mamed...oops, nope. Then there's Shankla...nope.
Nigel Short? An example from the 90s doesn't help your case. Gambits, when they are chosen, are selected not because they are slightly better, but because they are only slightly worse, as Pfren correctly implied
. So, yes once in a blue moon one will get pulled out, almost never in any critical game. The surprise factor and avoidance of prep has *some* compensating value. If you asked any super GM to play one of the aforementioned gambits repeatedly in a WCC match as their main weapon, they would laugh at you.