If your just using paint then it might be easier to draw the circuit out as a single line, rather than trying to keep a regular distance for a parallel line.
Scale is as you want it. The addition of a pit lane (the convention is to do it in red when using a single line drawing) tends to imply scale.
Take a look at this circuit from NickyF1 and you'll see what I mean:
http://tentenths.com/forum/showpost....75&postcount=1
Of the circuit itself, it's a good first effort. From the 90 degree right hander on the bottom left through to T1 it looks very much like Knockhill.
You can't do anything about it now, but you might want to read through the posting rules about the size of the image that you link to in that way. Post a thumbnail or just a text-link out to imageshack or wherever if the image is a bit big.