Cheerful, happy, and joyful.
In lines 140-150, what hasn't changed is that the father still switches off the electricity generator at 10 p.m. and goes to sleep in his study. The expression "as was custom" marks that this has not changed.
The language that shows that the father is changing can be found in lines 141, 173 and 175-176:
In line 141 we learn that he does not use certain rooms ("rooms we'd stopped using").
In line 173 we read that the father "seemed lighter" and chatted with his son.
In lines 175-176 the father says that "now he might be able to come to the end-of-the-year recital" at his child's school.
It says in your reading, so for someone to answer that we need to know the reading material.
The sentence that states to help save the day, here he must get past a scary three headed Guard dog. This is because in the Greek Mythological literature there are lots of creatures such as three headed monster’s like the guard dog.
