YOU SAID:

When I could scarce believe him mine:

INTO JAPANESE

とき私が乏しい彼を信じて私。

BACK INTO ENGLISH

When I believe in him scarce me.

INTO JAPANESE

私が彼を信じるとき、私は乏しい。

BACK INTO ENGLISH

I am scarce when I believe in him.

INTO JAPANESE

彼を信じるとき、私は稀です。

BACK INTO ENGLISH

I am rare when I believe in him.

INTO JAPANESE

私が彼を信じるのは稀です。

BACK INTO ENGLISH

It is rare for me to believe in him.

INTO JAPANESE

私が彼を信じることは稀です。

BACK INTO ENGLISH

It is rare for me to believe in him.