ionic bombardment process grants him superhuman strength, speed, endurance, invulnerability, immortality, flight, and energy-based powers to produce light, heat, explosive force, and effectively teleportation by relaxing into pure energy
First recruitment unspecified. Occasionally identified as an honorary member posthumously after his death in Avengers (1st series) #9. Became an in-house associate following his return in Avengers Annual #6, apparently given some sort of recognized status between #156-181 when he departed. Membership unequivocally official by his return in Avengers (1st series) #194.
Wonder Man was "dead" in an ionic chrysalis-like state between Avengers (1st series) #9 and #151. He frequently relied upon belt jets or a rocket pack for flight until developing the power of independent flight in Wonder Man #25.
Simon was killed again in an ionic bomb blast in Force Works #1. The Scarlet Witch inadvertently brought him back using her hex power in Avengers (3rd series) #2-3, first as an energy form, and later as a full human being with #11.
Wonder Man's powers and physical form were absorbed by Rogue in Uncanny Avengers (1st series) #21-23, leaving him trapped in her head. His mind was suppressed by a scientist working for the High Evolutionary in Uncanny Avengers (2nd series) #1, leaving him an unconscious and dormant presence in Rogue until she touched Deadpool in Uncanny Avengers (3rd series) #22-23. His healing factor severed the link between the two of them, once again manifesting Simon as an independent physical being.