英文书籍小王子第二章中一句副词和代词用法疑问

原文：

So I lived my life alone, without anyone that I could really talk to, until I had an accident with my plane in the Desert of Sahara, six years ago. Something was broken in my engine. And as I had with me neither a mechanic nor any passengers, I set myself to attempt the difficult repairs all alone. It was a question of life or death for me: I had scarcely enough drinking water to last a week.

The first night, then, I went to sleep on the sand, a thousand miles from any human habitation. I was more isolated than a shipwrecked sailor on a raft in the middle of the ocean. Thus you can imagine my amazement, at sunrise, when I was awakened by an odd little voice. It said:

"If you please-- draw me a sheep!"

"What!"

"Draw me a sheep!"

I jumped to my feet, completely thunderstruck. I blinked my eyes hard. I looked carefully all around me. And I saw a most extraordinary small person, who stood there examining me with great seriousness. Here you may see the best portrait that, later, I was able to make of him. But my drawing is certainly very much less charming than its model.

我的疑问1：certainly 是副词 very much是副词，less也是副词。这之间是什么怎么一个修饰关系？

我的疑问2：为什么这里用its，主人公已经看到一个小矮人在自己面前，这里为什么不用his？