He told her of feeling, which, in proving of what importance she was to him, made his affection every moment more valuable.

1. feeling 是否复数，之前应该有 his？ 等于说：He told her about his feelings.

2. which made his affection every moment more valuable. 非限制性定语从句。

3.  in proving of what importance she was to him，是定语从句中的一个成分，作状语，不是插入语。in doing...表示时间“在证明......过程中”。

4. of what importance she was to him 是一个名词性感叹分句，作 proving 的宾语。of what importance 是 she was 的表语。of what importance = how important.

5. made 接复合宾语。 his affection 为宾语， more valuable 为宾补。every moment 为 more valuable 的时间状语。