Fountain pens will easily handle that amount of writing.
The question is how will you handle that exam? If you stress out under pressure and start pressing the pen hard into the paper, that can damage the pen. Fountain pens are meant to have little to no pressure put on the nib.
If you press hard, I recommend a gel pen rather than a fountain pen.
I think you have to hold the pens.
I like how my Lamy Joy feels in my hand. It has the same section/grip as the Safari. But others just cannot use that grip.
I think you need 2 or 3 pens.
For something like this you need #1 a primary pen, and #2 a backup, and in this particular case #3 a backup to the backup.
Pens 2 and 3 could could be another fountain pen or gel pens.
When you run out of ink, it is MUCH faster to switch to pen #2, than to fiddle with and loose time changing ink cartridges and getting the new ink to flow.
So saying this, one option is to get the Lamy Vista and the Parker Vector, another is to get 2 Lamys or 2 Parkers (I carried 2 Parker 45s in college) that way you are not dealing with 2 different cartridges. I say Lamy and Parker because I know nothing of the Schneider pen.
As for the nib size. I used the old US Parker F nibs in college. That is equivalent to a Lamy XF nib. However the Lamy XF nibs that I tried, are not as smooth as the old Parker F nibs that I used in college. You will either have to smoothen the Lamy XF nibs or go up to a Lamy F nib, to get a smoother writing nib. But this will also use more ink. I think todays Parker nibs are like Lamy nibs, one step wider than the older US Parker nibs.