Yes you can as long as you earned it when you were Enlisted. You are authorized to wear up to 2 Warfare devices. If you have earned your SWO, then the ESWS must be worn in the secondary position.
Probably not, as only items specified in AR 670-1 are permitted on uniforms (see related link). Some units allow what's known as "local policy", and your chain of command may permit it as they see...