(a) と can be used for enumeration. Cf.this question. In this case, (an interpretation is) it combines objects for 込める. That is, を込めて is taking three objects (1)愛情, (2)尊敬, and (3)人間を超えた才能を持った人という気持ち.
(b) As Eiríkr Útlendi commented, you can think of the た indicating perfect aspect. Another factor may be that Osamu Teduka is no longer alive.
If there were a copula,
- 人間を超えた才能を持った人だった
- 人間を超える才能を持つ人だった
are both fine, but here there is no copula and using present tense sounds odd.
(c)という generally is like that which encapsulates the preceding sentence to make a clause. Here it makes a noun modifying clause for 気持ち: the feeling that he was a man with superhuman talents.