I'd suggest having a look at page 20 of your motherboard manual, which is online here.
According to the manual, it supports up to 4Gb DIMMs (not 8Gb DIMMs). Therefore, the only way to have the maximum 24Gb that the board supports would be to fill it with 6 x 4Gb modules. The most you could fit without replacing your existing memory would be 18Gb. I've got no personal experience of X58 boards, but my hunch is that as you have a tri-channel memory setup, you would probably need to add 3 more DIMMs rather than 2, to maximise the chance of it working.
For best compatibility, it's always recommended to fit matching DIMMs. Mixing different brands and/or speeds of memory in a computer can cause unpredictable results.
Crucial offer a compatibility guarantee which might be useful.
On to the main point, which is whether adding more memory would fix your freezing issues, it's just impossible to say without further information. Perhaps your system has other problems? Too many startup items running, junkware, malware, or hardware problems like overheating or a failing hard drive could easily cause the computer to be unresponsive. IME 8Gb is comfortably enough for Windows 8.1 for everything I want to run, so I'd imagine 6Gb should be enough for most uses. To be honest, I can think of no "ordinary" use that would need 24Gb! Your Resource Monitor on the screenshot above does not indicate it's run out of memory. "Standby" means cached memory, which is one of the things Windows memory management service does to try to improve performance. This memory can be made available for use by programs if needed.
If you can post a Speccy snapshot (using this guide) this will give us some more information to work with.