Bro, imo
- you didn't cause ammonia to spike which explains the reason why the process takes so long.
- fish died because cycling process not complete, not enough bacteria for livestock.
- nitrite and ammonia still exist which is toxic to livestock.
- I don't think you did a major wc to bring down nitrate after the cycle you said u succeeded.
- most probably you did not understand the cycling process, usually about 1 month.
- I don't think the liverock will still be there if u put it in sea.