The war was fought over territories. I dont think its uncommon to see treaties made that benefits the winning part and isnt as good for the loser.
The treaty was time-limited for 10 years to ensure that Mercinae as a city shouldnt have to pay for all time because their leaders of today wanted a war and lost it.
The offer of supplying you with food was meant as a friendly gesture. If you take offense in that its not hard to see why the peacetalks ended, eh?
Written by my hand on the 12th of Midwinter, in the year 971.