If the MC wants to avoid exile and death, then just... don't antagonize the Named Characters from the game? Don't be one of the villainess' lackies? This is the most easily avoided downfall of all time.
Why would the MC need to research how to cure Mana Deficiency when it was a condition/status effect in the game? Wouldn't there have been a cure?
Also the MC was a grown man of 35 years and then starts acting like a cutesy nervous child immediately? What is wrong with this guy?
Very odd story with multiple plot holes from the start.