How much theory can you remember at a maximum

I mastered that one years ago.

blundering is a way of life for me

I generally don't play alot of theory or theoretical moves in my games as I usually try to be the first one to play a move that's almost never or never been played through before e.g. In the Italian 3.d5!! has almost never been played or seen before and in the Vienna 2.b5!! has never been played or seen before ....

I used to joke about writing a book titled: "300 ways to not play chess.  Examples from actual play."

That's... interesting.

I have 2 possible books in the works.  Now if i ever decide to finish them?  That is the $64,000 question.

Don't know if you're a Spike Milligan fan...

When he wrote his memoires of the Second World War "Adolf Hitler, my part in his downfall", the dedication page said:

"After Puckoon I swore I'd never write another book. This is it."

I can remember that either the knight of the bishop moves in the shape of an L. 

in one line or two, maybe 25 moves deep. But i play a lot of weird stuff, so the odds my opponent will play a critical line that deep are almost nil.

Some openings are just so overanalyzed, you just have to remember that much to not get blown off the board. Rarer stuff can often be more forgiving

I have like 15 moves of Muzio gambit committed to memory for some reason but the openings I actually play I know until like move 11

Off the top of my head, I can remember 10 moves and some general ideas. In a 60+ minute game, I am confident that I would remember all of my prep, which admittedly isn't saying much, lol.

no I have around 25 in some lines

this exactly

I do not know at least 15

Queen's gambit Marshall defense. 

I know e4

wise words from the 1100 rapid

There's no reason to sit and figure out your openings at the board, when you could've studied your openings beforehand, and learned the correct ideas and general plans.

It would be like trying to take a test without studying, and trusting that you can just "figure out the answers", during the test, using your intellect alone.

Possible? Yes. But unnecessarily difficult.

Opening knowledge isn't the most important thing in chess, that's true. And some players approach it incorrectly (memorizing, instead of understanding).

But done properly, opening knowledge is an important part of chess. Neglect it, and you'll be putting yourself at a disadvantage from the start ...

He is correct to a point.  Obviously really spending time on the openings you play should start much earlier than 2500.  But with all the posts here from people that barely know how the pieces move and asking:

"What openings should i play?" 

Or the typical:

"Im an aggressive player..."

"Im a tactical player..."

All a waste of time.  If you cannot stop dropping material, missing simple tactics, don't even understand opening principles, or even have a grasp of the basics of the game.  Why are you wasting time on openings?  I asked a former IM coach when i should start to really work on openings?  His reply: When you start reaching a level of play that requires it.  Expert level.  Everything below that is all based on mistakes, blunders, and missed tactics.