The two men quarrelled bitterly and it was clear that the argument could only be settled by a fight.

1、that是主语从句.
断句如下：
The two men quarrelled bitterly
and (递进）
it was clear
that （that后面内容代替it部分的内容）
the argument could only be settled by a fight.
2、状语从句.
It was not until his third match in 1790
that
he finally beat Humphries and became Champion of England.A match was held at Stilton, where both men fought for an hour.这里的where是状从吗第二个句子不是定从吗？？Despite this, he was so extravagant that he was always in debt.这里的that呢1.是状从。2.不是定从。是时间状语从句的强调结构。可转换为he……，until……格式。3.be so……that，强调结构，引导目的。也属于状语从句。顺便说一句，1、如果不是为了应付考试，不要去研究这些。2、即便为了考试，也不要去深究。3、即便深究了，也不要太当回事。过去就忘了吧，否则太难受……