I have no clue what an attempted Windows defrag would do to a ext partition, but I can't imagine it would be good. I am not sure it would even try since Windows can't see or read Linux partitions natively anyway.
As for the swap thing, I always thought it was double, go figure lol.
This is a general rule of thumb, but there are other considerations too. Most 32 bit kernels are only compiled to recognize a total of 4 Gig. of system memory. Of this 4 Gig., 1 Gig. is reserved for hardware addressing. Most systems will only be able to use 3.2 - 3.5 Gig. Any additional memory will not be seen by the system anyway. The larger the swap partition is the slower it is. The total system memory, RAM plus
swap, should not exceed 3.5 Gig. Any more swap would just slow the system down and not be usable anyway.
When you start loading games on your Linux install a folder will be created in /usr/local called games. You could move this folder to your NTFS partition and rename it to let's say Linux_Games. You could then create a symlink in /usr/local called games pointing to the Linux_Games folder on the NTFS partition. Then when you ran or installed another game on linux it would use the Linux_Games folder on the NTFS partition as if it were the actual /usr/local/games folder.
To do that, let's say that the NTFS partition is sda5 and is mounted as sda5 in /media by putting the appropriate line in fstab and creating that folder in /media. If you don't know how to do that let me know and I will show you.
First move your /usr/local/games folder to sda5 and rename it Linux_Games. You will have to this with root privileges.
Then in a terminal:
This moves you to the /usr/local folder. The base formula for a symlink is:
ln -sf target_file/foldername symlink_filename
That is a little "L" in the ln
In your case it would be:
sudo ln -sf /media/sda5/Linux_Games games
That's it. You now have a symlink in /usr/local called games that points to your NTFS partition folder called Linux_Games that is used just like it was the real /usr/local/games folder.