HI Robert
Can/Should i just increase the size of the datastore on the EQ and in vSphere and continue to grow the size of the .VMDK's.
Always try to have all the datastores with the same size and around 10% free space. 2TB is a great size, if is possible don´t grow up more in this datastore.
Can/Should I move one of the .VMDK's onto a seperate datastore.
Yes, you can create/move vmdks to separete datastores, even if you have license for sVMotion you don't need dowtime
Should i just create a new .VMDK on its own datastore, add that disk to the OS, and move the files to it, then delete the old disk?
I' m not sure about the question, are you trying to solve the before question?
Regards