You can use "spread over", but not in your context.
Imagine butter "spread over" toast. That visual should give you a good feeling for the meaning. In your example, "the quantity of the hours" is the butter, and "2-8 hours a day" is the toast. But since 2-8 is the actual "spread" the sentence just doesn't hang together semantically.
Here's a reword of the final sentence:
The testing took place in segments of 2-8 hours per day.
BTW, "tested and evaluated" is somewhat redundant. Yes, an evaluation may not include a hands-on test, and a test might not include an evaluation of the numbers. Nonetheless, together they sound redundant.
Here's my suggested rewrite:
The system review
sidestepped the whole "tested and evaluated" question
took more than 80 hours. Fifty hours were used
dropped the first phrase to remove the repetition of "hours"
for the implementation phase
put implementation first because it came first in the sequence
and 30 hours for the final evaluation.
switched "final" (adjective) for "end" (noun).
The testing took place in segments of 2-8 hours per day.