What battery are you flying it on? Also look at your throttle calibration plus the settings in Betaflight.
Generally Bullnose type props will provide more thrust at the expense of efficiency, more thrust will help hovering.
Also make sure you are out of ground effect, as you won’t get a smooth hover in ground effect.
The props shipped with it are known to be rubbish. Any set of 5040’s will be better. The Gemfan tri blades are good value for money, there’s a couple of different blade profiles at similar prices.
That should be enough power, but remember what @ElectriSean said yesterday about weight.
All the info on this quad says the factory props are poor! There’s a ton of mod videos on it, Josh Bardwell has two on his channel that looked good.
No, that would be a parallel connection, giving you 5000mAh @ 7.4V
To get a serial connection, you have to connect the red from one to the black of the other, then connect the PDB to the remaining red & black. That is a HUGE amount of battery for a 5" quad, I'd recommend getting some proper 4S 1300's.
Have you plugged it into Betaflight, props off, to see if when you give a stick input, you get an output from the FC?
The way to solve these problems is to work logically through them, which is very nicely illustrated in the linked video.
The data flash chip is for black box recording. If you just reset the FC to deafults you will have to go through and reconfigure the ports and Rx settings. Not usually the recommended first step in solving a problem If you can, find a copy of the stock configuration otherwise you're going to have to have a close look at the connections etc. to figure out what's needed.