Why did Easter Sunday become a problem for Jess's family?
In Chapter 8, we learn that Easter Sunday is now a problem for Jess's family because the father has just lost his job, and now there's no way they can get new clothes for the kids like they usually do before attending church on Easter.
That whole tradition of getting new clothes especially for Easter is really important to Jess's mom: the narrator tells us that she spends time and money on it because she wants to be proud of how her family looks, which is rare.
So the loss of the job, and the impending inability to attend church on Easter in new clothes, stirs up a ruckus in the family--the older girls get very upset, since they really care about getting new things and looking pretty, and their father fusses at Brenda for making a foolish and dishonest suggestion. She wanted to buy new clothes, wear them to the Easter Sunday service, and then return them to the store.
Jesse just hates the uproar and can't wait to escape to the barn to quietly milk the cow. He's worried about Easter Sunday, obviously, but he realizes that the problem is bigger than that. The loss of his father's job means the family is really in trouble.