How to run Ubuntu 14.04 on ASUS X500CC using only discrete graphics card?

Question

ASUS

Yes:
ASUS X550CC (core i3-3217U (HD4000 + GeForce GT720M), 4GB, 750HDD, Ubuntu 14.04 x86-64).
Video works fine out of the box on the integrated video core in the processor.
Want:
Switch to discrete graphics. I work from the network. I want the maximum RAM for work, in the BIOS I allocated 64 megabytes for the video.
Tried to do so:
1 option. Immediately after installation, I install Nvidia binary driver 331.38 in Additional Drivers. After reloading I get brakes, blinking, windows float when dragging. I lose the ability to control the brightness.
In the Nvidia control panel, I see that the prime has switched the video to a discrete card, I see its frequency and temperature. Also the inscription No display. Accordingly, I can’t change the brightness at all (not with hotkeys, not through the settings - (I get a system crash).
Option 2. I download the .run file from the official site, install it, follow the instructions (331.68).
After a reboot, I get everything described in paragraph 1.
3 I do this:
sudo apt-add-repository ppa:ubuntu-x-swat/x-updates
sudo apt-get update
sudo apt-get install nvidia-current
sudo apt-get install -f
sudo apt-get update && sudo apt -get upgrade
sudo apt-get autoclean
I get everything from point 1.
I just want to switch graphics to discrete, I don't need the built-in kernel to free up precious RAM for work. Tell me how to get what you want?
Thank you. Sincerely.

Answer 1

Optimus is designed to make the most of integrated graphics. I see two possible solutions:
1) Buy more cheap memory (preferably)
2) Install bumblebee (as a normal, stable, working solution that does not require X reboot), and try to modify the X startup scripts so that they run from under bumblebee. There is no way to turn off the distrito, the picture still passes through the integrated card.
3) If you sometimes use heavy applications in terms of graphics, install bumblebee, and run through it only those applications that you need (this is provided that in normal mode 64 MB of video memory will be enough for you).