어법질문드릴께요..

1. joseph miller and his grandson eric said that the boat lost power about 4p.m. on thursday andthat/what they were unable to get the engine started again.

that/what 관계대명사를 묻는것같은데요..
답이 that이더라구요. 여기서 that이 접속사인가요? 관계대명사인가요?
그리고 what이 안되는 이유는 먼가요... .

2. the small boat was found drifting about five miles off cape cod. the victims were all taken to memorial hospital where/which they were said to be in fair condition.

where/which
답이 where인데요.. 앞에 memorial hospital을 선행사로 보고 where뒤의 they were said to be in fair condition을 완전한문장으로 봐서 관계부사 where이 온거 맞나요?
해석을 했을때는 hospital뒤에 , which 써서 계속적용법으로 해석.. 그러니깐 희생자들은 memorial hospital로 모두 데려갔고, 그곳에서 그들은 좋은 상태가되어질것이라고 말했다.라고 하면.. 이상한가요/?
그리고 where 뒤의 they는 누구를 말하나요??

that/what, where/which 가 왜 that과 where인지와 what과 which가 답이 안되는 이유좀 알려주세요..ㅠ