Okie, so! I see it is a memory issue! Sadly, Tjm, you will have to raise your memory. I can tell it's hardware due to how you are on 64 bit, are still getting out of memory errors, and that restarting the game "refreshes" how long until you have to restart again.
Gmod is VERY unoptimized for new systems. Due to the unoptimization, the game is using up memory and the computer can't purge it quickly/at all, using all of the physical memory. This is where your virtual memory comes in. When the virtual memory comes in your game starts to slow down, which you see before it's crashing. Virtual memory is much slower than physical, so the game slows down. You can keep playing with the virtual memory until it, too, runs out. When the virtual memory is running out, your game crashes (so that all the memory it's used can be purged. Restarting the game purges the memory, too, making it "refresh").
On a side note, replacing your hard drive with a solid state drive will also fix this issue. An SSD can run virtual memory almost as fast as a memory stick, since an SSD is basically a giant memory stick. An SSD will load programs on it INSANELY faster (by insanely, I mean anywhere from 8x faster to 30x times faster) (because an SSD has no moving parts, it doesnt have to rely on physical boundries as much as a hard drive that has a disc. Allowing it to process and load info much faster than a disc.), which can reduce the load on your memory cards, possibly even allowing them to not get entirely used if your SSD is fast enough.
I have replaced my 1tb hard drive with a 1tb Samsung 860 Evo SSD, and replaced the 8 gigs of memory I had with 16. Since I had the SSD, I have seen MUCH better performance. SSDs can be expensive, but beneficial (For price ranges, get your current specs, and look online for an SSD, they can be atleast 100 dollars. Also, the more space on an SSD, the faster it runs, since the more empty data there is, the less it has to process. NEVER CHEAP OUT ON COMPONENTS).
Memory can also be expensive, but not as expensive. Know how I said an SSD is basically a giant memory stick? It is. Only difference is that most forms of memory temporarily hold data until they stop getting power, and an SSD can permanently hold it whether it has power or not. An SSD is just a giant memory stick in a different form that uses more resources, making it more expensive. Memory sticks are usually 40-100 bucks. I recommend 16 gigs of memory for gmod. BE SURE TO LOOK AT YOUR SPECS AND ENSURE EVERYTHING IS COMPATIBLE BEFORE PUTTING NEW COMPONENTS IN! NEVER CHEAP OUT (get onbrand stuff from onbrand stores with good reviews)!
Tl;dr, you need more memory, an SSD, or you need to deal with it, sadly.
