Ekev

...[G-d] WHO FEEDS YOU MANN IN THE DESERT, WHICH YOUR FATHERS KNEW NOT,  TO AFFLICT YOU AND TO TEST YOU... (Devarim 8:3).

Is there a difference between "afflict you"and "test you?"

The Mann G-d sent made life both easy and difficult.  They had daily livelihood with minimal effort.  On the other hand, they suffered anxiety wondering whether Mann would come the next day; they had to develop trust in G-d.  Poverty and wealth both test a person's loyalty to G-d, each in its own way (Sforno).

FROM THE DAY YOU LEFT EGYPT UNTIL YOU CAME TO THIS PLACE, YOU HAVE BEEN REBELS TOWARDS [literally "with"] G-D (9:7).

Were the Jews actually guilty of continuous rebellion?

"Rebel with" is a peculiar expression in Biblical usage.  It does not mean rebelling against  G-d.  It means they were never entirely with G-d. On the positive side, even in moments of rebellion they were still with G-d to an extent (Rav Hirsch).

AND NOW ISRAEL WHAT DOES THE L-RD YOUR G-D ASK OF YOU EXCEPT TO FEAR THE L-RD YOUR G-D TO WALK IN HIS WAYS AND TO LOVE HIM AND SERVE THE
L-RD YOUR G-D WITH ALL YOUR HEART AND SOUL (10:12).

The words "what does G-d ask except" seem to suggest that G-d asks little.  But what He asks for seems to be a  lot!

Consider what the verse excludes.  G-d asks that we do His will.  We do not need to be concerned about anything that is not His will.