re: Am I buying too much house?

Prima facia the answer is in the negative as you are unmarried and at those numbers.
That's simply too much RE debt for my taste in most areas of Louisiana as the area's aren't appreciating enough to justify the investment. Uptown NOLA is an exception.

But here's an alternative?

You are in a family business and making $120,000/ year.

Is there someone associated with the family business (grandparent, parent?) who can gift money to you in lieu of salary? Depending on how generous they might be there are several possible scenarios:

Very generous:
Each generous person can legally tax-free gift to you $14k in 2015. You apply this amount ($14k or $28k) amount directly to a $280k mortgage and you are in much better shape.

Less generous:
The gifted amount is subtracted from your wages but obviously no payroll taxes or FICA, etc is taken out. I know that Social Security taxes stop after $105k annual wages or thereabouts so that portion won't be negated unless you get under that threshold. You could artificially lower your company wages on paper to $100k and have someone gift to you the $14k and be ahead of the game as you'd have less income tax liability at the end of the year, and the company would pay less salary and payroll taxes. Win-win.

And then this opens the door to the discussion of maybe not dollar for dollar to your wages, just gift you some damn money. If there is more than one person to gift to you then you can really make some hay over five or ten years on a house mortgage.

This obviously presupposes that the donor(s) eventually want(s) you to inherit little/some/ much/all of their estate(s).(!)

A tax professional is going to tell you that it's probably legal but he/she wouldn't recommend you do it.
Whatever.
Consult any/all of your legal and tax professionals before doing anything like this.