Yes, it will work for both 450 Busmaster and 458 Socom per Kak’s website.
Yes, it will allow .300 blk (30 cal.). "The bore will allow a 45 caliber to pass through"
Yes, this KAK Extended 5/8-24 Flash Can will fit and function as intended with your PSA 308 rifle.
This is the typical thread pattern for .308 or AR-10 barrels. If you're needing a KAK Extended Flash Can for a 5.56, you most likely need the 1/2x28 thread pitch. You can find that flash can at the link below.
https://www.opticsplanet.com/kak-extended-1-2-28-flash-can.html
This will fit as long as your barrel is threaded 5/8x24. Most AR-15 barrels are threaded 1/2x28, so you will need to find out how your barrel is threaded in order to be sure. If your AR is threaded 1/2x28 then this one will fit: https://www.opticsplanet.com/kak-extended-1-2-28-flash-can.html
The bore will allow a 45 caliber to pass through. A .45 ACP has a diameter of 0.452", and the .458 SOCOM has a diameter of 0.458". This is not large enough for a .458 SOCOM.