with the stock motor that is about all you will get  the motor from what i have learned is actually a 500 watt that peaks at 750.  i upgraded my controller and motor and i peak around 1100.  Area13 is where i got my upgrade parts.

buy a different brand like WIRED bike.  lots of power and much bigger battery.  $2000.  sell what you have and buy the wired.

yes my error....chain

WD40 works great for cables.

Nothing wrong with being short.  But my understanding is that 22" tires are not common.  You will have problems with tire replacement.

I had an issue with a dirty chain.  It would click.  Once cleaned no more clicking.

Maybe an aftermarket controller will solve the problem.  Check out Area 13 for Rad controllers.

It wasn't difficult but it had it's challenges...mostly pulling a wire or two through the frame.  It was 3 years ago.  I think it is more of a pain to remove the rear wheel than the controller.  I have a Rad Rover 5.  Maybe the newer models are different.

probably power settings.  hold the upper and lower buttons for a few seconds to access the settings.  you might reach out to Rad for the correct settings.  also check youtube for how to change and access settings. 

I'm sure you could get one from Rad sent to a US address.  But you will probably pay less from another company.  It is a relatively simply process to swap the controller out.  I bought the upgraded controller that unlocked a bunch of torque, but after I purchased an upgraded motor is when I really saw top end speed increase.  Doing so will drain the battery faster. 

you can find them sometimes on ebay.  Try Area 13 for an upgraded controller.  I think they have it now for your model.  I know at least one company is selling the upgrade, but I don't recall which has it. 

I see them for sale on eBay from time to time.  Unless you are concerned with customs, you might give eBay a try. 

I recommend Tannus Armor inserts.  Since I have installed them I have never had a flat.  But without them I had at least 4 flats on the rear wheel and I was tired taking the wheel off the back.  It is a pain in the butt.  The front tire I have never had a flat and I have over 4000 miles on it.  I was waiting to replace the tire on the front to add the Tannus.

Probably but I would consult Area13 formally Bolton Bikes.  They will have the best answer for you. 

I would say if Rad wants to charge for something like that, but aftermarket.
Aftermarket will probably be better quality anyway.