Actually there are some saying we should have run exclusively.
I have no problem with the thought that maybe we could/should have run a little more, but I can't fault Garrett for small differences in the run/pass ratio. Either you make the decision you can sit on a lead with most of the second half or you decide you still have to move the ball and put together some drives, and if you choose the latter, which I believe is the correct choice, then you are going to have to pass. I'm not going to quibble over what the ideal pass/run ratio would be, and besides, I feel a lot depends on what has been working, the feel the coach and team have for the flow of the game and other factors. I don't know that there is a magic ratio.
As for the last INT, keep in mind that while it is true that Detroit scored with a minute and a half left, they got the ball with 4:13 left. That means if we had run off the additional minute and a half you mentioned, Detroit still would have got the ball back with 2:48 left. Not a lot of time, granted, but keep in mind Detroit didn't necessarily have to score a TD. All the had to do was get into FG range to tie it up, and Garrett had to be mindful of preventing that as well as preventing a TD.
That said, I see an argument for your position on the possession where Romo threw the last INT, but I don't see that there was a clear cut decisioin either way. Run and punt and you run a little clock but still give the Lions almost 3 minutes to move into FG range and tie the game. Pass and there is somewhat more risk of a negative play, and somewhat more chance of sustaining the drive and running out the clock. Seems like a pretty close call to me, and I don't think I would condemn Garrett either way.