Result Summary preview responsive design

I have tried my best with my basic knowledge.

Here are the few things I wanted to know:

1. Whether to have fixed width like I used 350px. Best way to use rems if I have to use them.
2. To make both of the summary and results div(look into my code) look same height, I have extended my padding, Is this the correct way or should I follow any other best practise?
3. Please let me know if I should develop or learn any standard way to make it more efficient.

Thanks, Kiran.