There's no in-canon reference for either, however I think there are strong points for Zapathasura to not be a wight.
First, a breakdown of the history before Zapathasura awakened:
- Ravnos and Kuei-Jin were fighting it out for quite some time in India
- Ravnos were on the losing side and decided to use mass embracing as a tactic
- The fighting became bloodier, with the new embraces dying almost as soon as they were created. Each death releases a "death cry" through the generational lines. This cry slowly crawls up the generation ladder. What exactly is contained in this cry is unknown.
- Methuselahs awake due to the massive amount of Ravnos that die
- Zapathasura awakes
Zapathasura awakes because thousands of his children have died (for humans probably equivalent to a massive cluster headache). Its bloodline is in danger of extinction.
This leads to the second part: the Week of Nightmares (see the "Time of Thin Blood"), summarized below:
- Zapathasura is hungry, so It snacks on everything nearby (and due to age it most likely needs kindred blood)
- Goes on the counter offensive
- Is confronted with three Kuei-jin Bodhisattvas (≃ Eastern Antediluvians), a mighty brawl ensues
- The Technocracy says "Nope!" to the brawl and uses magical neutron bombs and orbital mirrors to wipe everything away.
- In Zapathasura's dying moments it calls Its blood back, which causes all surviving Ravnos to go into a blood craze (= Frenzy).
Sidenote: we're talking about an Antedeluvian, walking plot devices... We're ants compared to a being of that level.
Onwards now, to tackle the post's points:
- Appearance is irrelevant for a being with Chimestry 10. Zapathasura can look however It wants to look.
- I would think that Zapathasura follows the Eastern version of the Road of Paradox (probably my personal opinion)
- For the lacking of social skills: see above (the infamous death cry could have given it a good idea of what was going on) and with Animalism 10 does It really need to interact with anybody to learn something?
- With regards to the killings: see above