Only showing 3 restore points

I am having some issues playing Starcraft II that I didn't use to have when I first assembled the computer. I wanted to restore back to where I was several months ago, but the restore point isn't listed in System Restore. In fact, only 3 restore points are offered and they are all in the last few days.

I looked at the space available to save these restore points and it was only using 1.59 GB of an allowed 2% which is 10 GB.

Why would the older restore points have been deleted if the max space wasn't reached?

Yes, I am checking the box "Show more restore points"

Do you use any cleanup or optimization programs that might delete restore points?

I create system backup images using programs such as Acronis or Macrium.
imho backup images are more reliable than restore points.
You can control how long to keep the backup, what to include and when to create the backup.

I know this doesn't help with your immediate problem, but it's something you should consider and learn to use going forward.

A couple of tutorials about imaging:
Imaging with free Macrium
Backup Complete Computer - Create an Image Backup

You can also take a look at the Sticky Threads in the Backup and Restore SF forum.