So after lots of measuring, I would need a 1/2" spacer to center the tire/wheel between the fender and the spring. Can I safely run a spacer that thick?
You might need a 1/2" spacer to center the wheels but you probably only need another 5/16" to 3/8" to get them to clear the springs without rubbing, looks like you've already got about an 1/8". As far as safely, yes, you can run a spacer that thick as long as your have lug studs that are long enough and everything stays hubcentric. I'd prefer some aftermarket lug studs too, and since it appears you're racing you may already have those anyway. You should also check with your class rules to make sure you'll pass tech if you need to.
If you have BBP axles you might need to take a little sandpaper to the hub bore on the spacers, they're 70.5 and the registers on the BBP axles are usually ~71mm. But the spacers will be hub centric. Here's a set of 12mm spacers if you really want to center the wheels according to your measurements. I personally just try to run the spring clearance at the minimum I can get without rubbing, you typically need more clearance to the quarters than the springs because of the body movement.
