The size sounds great! 1200 sq ft is plenty, fits a good number of people. Just don't fill it with excess furniture, knick knacks, etc. If layout demands, you can be creative with how each space is used. (The decluttering thread just had a great account on what a bit of rearranging did to one family's space.)
So, the size I think is dandy, generous even.
You can always create a fourth bedroom/studio/den/office on the acre -tiny house, shed, sleepout, RV, whichever.
Your not loving the place is more of a concern to me. There's been lots of discussion on the forum re: we should not buy a house according to feelings of "in love" yadda yadda. At the same time, a huge and long term investment should fit for you every which way, including emotionally (at the very least a peaceful acceptance).