Hey @candiceliu93
I donâ€™t have access to the given course attached. So I am gonna base the response on my own course notes/ practice notebook.
Letâ€™s go in reverse order.

degrees of freedom: Following links can help you understand this in more detail and with the content of how to explain/ define it.
Letâ€™s see the example given in course. This is how the observed values look like:
The green colored cells here represent crossjoint distribution and the red cells indicate the marginal distribution. For a tabular data like this we calculate,
dof = (rows  1) * (columns  1), where rows and columns do not include the marginal distribution. This will give us dof = (2 1) * (5 1) = 1 * 4 = 4
Now to answer the question what does it actually mean? If we observe the following table, we would needed minimum of 4 values to identify the rest of the values ("?")
.
If we go any below than 4, we wonâ€™t be able to calculate the rest of the values. That is minimum no. of independent variables we should know is 4. (the second link gives you multiple example to elaborate this!)
pvalue and alpha: Well here is where you are slightly mistaken. The pvalue that is calculated is 5.192061302760456e97. this pvalue is not 5.19. Itâ€™s actually 0.000.
The general rule we have is this:
 if pvalue <= \alpha (which has to be predecided and should not be varied based on pvalue obtained!), we do not have statistically significant results to support H_0 and so we can reject it. We accept the H_\alpha
 if pvalue > \alpha, we do have statistically significant results to support H0 and so we cannot reject it.
So based on the result we have got, we can that we reject the H_0. We can say that at 5% significance level we cannot support Gender and Race do not have an impact on Income. In fact they actually do!
These links are helpful but may not clear all your doubts and thatâ€™s okay. Do let know in case you need more help on this.
Just in case a discussion with another DQ student is here