程度, 程,ぐらい differences, nuances

Question

秋葉はシキから、何かの悪霊じみたモノを受け継いでしまった。 簡単に言うと、ソレは秋葉に移った時点でとても薄くなっていて、秋葉の性格が少し強気になる程度の影響で収まった、というのだ。
それが原因で秋葉は暴走してしまったワケだけど、あの一件の後、秋葉はソレの手綱を握ってしまったらしい。
……強気というよりはいじわるになった、というのが正しいと思うのだが、本人に言うと怒るのでやめておく。

Akiha inherited from Shiki something like an evil spirit.
To put it simply, when it transferred into Akiha it faded and the influence on her personality was that she became a little more confident and nothing else. (lit it calmed down).
That was the cause for her reckless behaviour but, after that incident she put it under control.
I should say that she did not become more confident but more bullish, that would be correct I think but, if I said that to her she would get mad so I gave up on that.

I am not sure if I am understanding how 程度 works. It's a noun and I think it works this way.

簡単に言うと、ソレは秋葉に移った時点でとても薄くなっていて、[[秋葉の性格が少し強気になる]>程度の影響で収まった]、というのだ。
So all those things in the [] modifies 程度 which refers to 影響.

影響 can mean influence or effect. What I do not understand is if it should be translated like.

The degree of the influence of the spirit was so little that it only made her a little more confident and it stopped there

or

Her personality become a little more confident to the degree that she was able to calm it down.

So how does it work?

Could I use ほど or ぐらい instead?

簡単に言うと、ソレは秋葉に移った時点でとても薄くなっていて、秋葉の性格が少し強気になる程の影響で収まった、というのだ。

簡単に言うと、ソレは秋葉に移った時点でとても薄くなっていて、秋葉の性格が少し強気になるぐらいの影響で収まった、というのだ。

I know that 程度 is a noun ほど and ぐらい can be particles and nouns if I am not wrong. What are the different nuances?

Answer 1

They are synonyms by themselves, but have different nuances when used as formal nouns (though all translated as "to the degree").

• X 程度の～: suggests the degree of X is smaller in magnitude, amount, seriousness etc. than you expected

• X 程の～: opposed to 程度の; the degree is bigger in physical or mental impact than you expected

• X ぐらい（くらい） の～: neutral about X's significance relative to your expectation

So, in this case, since 収まる implies "don't go any severer", 程度 and くらい would fit well, but 程 would sound awkward.

Answer 2

程度 has the most neutral nuance of the three and is open to the widest range of interpretations. It can be substituted for either, but most often it is seen as closer to ぐらい, as neither implies a subjective view that the extent is seen as large or small. The difference is that ぐらい is associated with some form of uncertainty, while 程度 on its own is not.

ほど "to the point that..." implies the upper limit of the extent, so it would be more logical to use some conjunction between the two phrases to suggest why it is relevant here to remark on the magnitude of 影響:

• ソレは秋葉に移った時点でとても薄くなっていたが、秋葉の性格が少し強気になる程の影響で収まった