I agree with the anon above. There is no subjunctive there. There would be a subjunctive if it were rewritten like this: "We were required that we go to the store to buy food." I corrected it. It should be "to buy", not "and buy". Here, "we go" is subjunctive.
The "I own/I owned" subjunctive comment could have been explained better. I know the subjunctive so I got your implicit meaning, but others might not understand it. You should have explicated this concept more. I would have if I had written this article.
All in all, not bad. If I were grading this, I'd give it a 7 out of 10 on the subjunctive.