Q: What type of 5/8" thread is it - if it is not a standard NPT?
Is it BSP? Is it MPT?
Q: Can you attach this pump to a normal sanke D coupler or do you need an additional adapter?
A: this would need to be done using the pump adapter part#40-1917
Q: How would you go about connecting this to a keg?
A: This adapter C009-3382 can be used to connect the pump to a pin lock or ball lock disconnect
Q: Whats the thread size and is there some sort of check valve built in?
A: The thread size is 5/8" but is not a standard NPT threading. There is also a diaphragm inside that acts as a check valve on the pump