What's the difference between degree and grade?

Degree is not an appropriate word choice here, nor is it one I have encountered as a native English speaker. The 105 in your example sentence should be a grade or a score (most likely an average or cumulative grade).

You can earn a degree of a certain type (a bachelor's degree, a degree in physics) but not of certain score.

In some situations (a low-grade job is like a job of low degree), degree is a synonym for a grade, but this is not one of them.

Looking at definitions of degree in the Oxford dictionary, any acceptable usage of degree with a number is limited to usage as a unit (100 degrees) or a specific term (second-degree murder, first-degree burn).