In my heart was a desire to live more dangerously. I was not unprepared for jagged rocks and treacherous shoals if I could only have change - change and the excitement of the unforeseen.

1）In my heart was a desire to live more dangerously 是不是少了不定式的形式主語it, 即In my heart was a desire to live more dangerously ?

2)  if I could only have change 這里could是表過去的能力還是過去的推斷呢？ 另外這里的only是加大語氣“只能，別無他法”的意思吧？


1 In my heart was a desire to live more dangerously. 

這是一個完全倒裝句，介詞短語作表語前置，主語后移。不定式是desire的定語，不是主語。

2 could不是表示能力，更不是表示推斷，而是表示客觀條件允許，即所謂理論上的可能性。

if I could only have...= if only I could have..., 只須...， 引導條件狀語從句，表示充分條件。