Looking at your pictures and those for the EX, it looks like you have the EX...but you said the rotor diameter is 300mm and the EX has 350mm. Either way, you have a great deal there. But you had better determine which version you have so you get the right parts.
As for your questions:
1. When you straighten the blades out, you want them to be tight...a real snug tight...not destructive tight...if you know what I mean. If the fold back on impact with something...that is not a bad thing...but they should not fold back in flight.
2. The paddles need to be flat to the plane of the holder they pass through (not sure of the proper name). On the rotor hub, the frame that that paddles pass through...the paddles should be flat to that plane. Note, you can adjust their angle to change the characteristics of flight, but I do not recommend doing so until you have the basics covered. Heck, I am still learning them...and thus my advice is that of others and my limited experience.
3. The canopy should stay on by the rubber grommets attached to a spar on the frame of the heli.
4. You shouldn't need to worry about rebalancing with the heat sinks. The thing was designed with them in mind. So go ahead and use them.
5. The transmitter. The four switches in the center near the bottom. Those are servo reversing switches. Do not play with them unless you want stuff backwards. The left toggle swith should control the main rotor and tail rotor (if it is set up like my own). The left toggle in the vertical plane will add throttle and thus create lift. When it is moved in the horizontal plane, it controls the tail rotor...by either increasing or decreasing its movement. This one stick controls the up and down of the heli and the yaw of the heli (as in its rotation about the vertical axis). The right stick controls the forward and side-to-side movement of the heli. It does this by adjusting the plane of the main rotor. When pushed up, you should see the main rotor tilt toward the front of the heli. When pushed to either side, you should see the main rotor tilt in that direction. When pushed down, you should see the rotor tilt toward the tail of the heli.
The little switches beside the two sticks are the trim, switches for the respective stick and direction.
These things being as small as they are do not require massive stick inputs. A little twitch is about all it takes to send these things flying out of control...for us novices.
If the thing came with a manual, read it...then read it again, then re-read it....
Here is a PDF version
I hope this gets you started in the right direction. Be prepared to replace rotors regularly. Once the get dinged up the heli gets harder to fly as the rotors get out of balance.
Have fun.
