I noticed an interesting thing about the releases of several traditional bowlers who are between 215-232 average in my league. They all don't have text book releases.  All have similar release to mine, or are even higher on the ball than I am. One bowler who is the top bowler in the league has a suite case time of release. Then you have the spinner types. I don't see a Barnes or even a Duke type of release, yet they all pretty good. Then there are those similar to mine, it's not perfect, but it best for their game.

These guys and a gal repeat their approaches, are very accurate, with speed and medium to high rev rate, and are straighter players. Male versions of the P-League

Maybe I'm trying too hard to be "text book" that it's hindering my improvement process.  I'll probably never get back to being 210-218 again if I keep trying to be "text book", or something I'm not. My average even dropped 4 to 6 sticks since trying to fix things - shot 585 this week...

Side note:
About my back swing going inside my head at the top, somehow I was able to straighten out my swing by changing how I held the ball at set up and the direction of my push away. I don't know how it fixed my swing, but I went back over a decade ago (video archives lol) and copied how I held the ball back in the day when I had a straight swing and a release the kept my hand behind the ball longer.

At a certain point, the idea of inherent talent must be discussed.

Top league bowlers all have one thing in common.  The ability to consistently repeat shots.  The difference between what you are seeing from a variety of league bowlers styles and what you see from pros is that pros have a release that is more versatile in its reaction to varying conditions ( particularly length ). 

Many people think that house shots score high because they reward inconsistency.  Not true.  House shots require consistency to score well over a number of games.  However the extremely crowned oil patterns allow a variety of styles from full roller to spinner to all find a place to play and be successful.

+++1

What the best pros have learned is how to cut down axis rotation without sacrificing revs.  Its rev rate that enhances carry, not amount if hook.  By keeping your angles more direct with a higher rev rate you maintain versatility without sacrificing carry.