TE 511 2013 power band

OK so i just did my first ride on a 2013 TE 511 almost new bought used with 200 miles so i customized a few thing to suit my size and riding style I still have a couple problems I need to address Im 6'2" and can still barley swing my leg over the back and for single track trail I need it 1" lower and the power band is sharpe and jerky and when I let the throtle off Its like trowing out a anchor when relaxing standing up it puts me over the bars! The suspension was fine took jumps and whoop de doos great.

Probably need a fuel controller. I've been very happy with my PCV. It may allow you to fiddle with the decel characteristics. Will definitely smooth out the acceleration and give a gob more power too.

The 449-511 engines usually have very tame throttle response from new.
What mods had the previous owner made?

Possible they removed the secondary butterfly for improved throttle response and may also have removed the idle control cam roller from the throttle shaft to stop a fault where the idle speed hangs on closed throttle.
Try raising the idle speed a little to reduce engine braking.
As for the engine power, you'll get used to it soon enough. These engines are a friendly engine to ride.

Also, you do not need a fuel tuner box for these bikes any longer to change fuel and ignition mapping.
The excellent TuneEcu app for Android and a few plugs/leads will give you total access to the ecu parameters.

On the height of the bike, I'm at a loss.
My 2011 TE449 is actually taller than the later models and I'm 5'11".
I have no trouble with the height of the bike....
Perhaps your legs are mounted a little closer to the ground??