Algorithm: How to use x and y mouse movement co-ordinates to generate random data? Background:

I'm making a program for fun as a learning exercise. I want to generate some actual random key material (not pseudorandom) from a JavaScript program. For my program is just for encrypting/decrypting plain text letter by letter so I've chosen to use the ASCII printable character set (what characters you can type on a standard US keyboard) which gives 95 possible characters.

I want to capture a users' random mouse movements on screen to capture a long stream of random numbers. I want to use the x &amp; y coordinates from each mouse position out of a possible screen resolution of 1920x1080 pixels and then map them back to a character within the list of possible ASCII characters. Then I can use that character in my key material. Let's say the program captures the following series of x and y coordinates like so:

[478,702]    
[503,701]    
[581,687]    
[633,670]    
[691,646]    
[757,620]    
[814,599] 


Question 1:

At this point should I multiply the x and y coordinates to get a better random number, ie 478 x 702 = 335556 and use this number? Because if I just took the x number separately then you might end up with consecutive numbers e.g. 121, 122, 123, 127 as they're moving the mouse in one direction which doesn't look particularly random. Or should I add the numbers together ie 478 + 702 = 1180? Or perhaps alternate between adding and multiplying for each set of coordinates I get to make the random number?

Question 2:

Now what's the best way to map the random number to a character in my list (array) of possible characters? If I've got an array of all the 95 characters [0 - 94] for a zero based array, and lets say my random number is 1180, how do I map that back to a character in my array? Do I loop over the array multiple times until I'm at the 1180th character and now use that character for my key? Essentially this would be like repeating the 95 possible characters in a row up to 1180 characters, then taking the last one. Or maybe you can work this out mathematically?

Or do I create a big 2D array with all the characters repeated horizontally and vertically (like a big grid to match the screen size), then when an x and y mouse coordinate comes in I map it to the x and y indexes in the big 2D array and use that character?

Question 3:

What is the entropy quality of the random numbers generated from the mouse movements? Does mapping it back to the reduced character set reduce the entropy? How can you make the process of capturing random data from the mouse movements better?

Question 4:

If my screen size is 1920x1080 pixels and I pull out an x and y coordinate from that. What is the search space ie $2^x$? how do you work that out?

Many thanks
The PuTTYgen program, which is open source, contains the following comment in WINPGEN.C where it collects mouse movement for key generation:

/*
* My brief statistical tests on mouse movements
* suggest that there are about 2.5 bits of
* randomness in the x position, 2.5 in the y
* position, and 1.7 in the message time, making
* 5.7 bits of unpredictability per mouse movement.
* However, other people have told me it's far less
* than that, so I'm going to be stupidly cautious
* and knock that down to a nice round 2. With this
* method, we require two words per mouse movement,
* so with 2 bits per mouse movement we expect 2
* bits every 2 words.
*/


I don't know how accurate this information is. I just remembered seeing it and though it was worth sharing.