I don't mean to sound all preachy or anything, so I hope I'm not coming off as a total B, Steph.
With the additional info from your first pregnancy, yes, it's possible to really fail the 1-hour and pass a 3-hour test. And honestly, there are a lot of false positives with the glucose tests that can be based on regular diet. For example, high protein diets like what is recommended with the Bradley Method of child birth has a very high false positive rate on glucose tests. But like you said, you'll never know about your first pregnancy. With the 3-hour test, it's very possible to have an abnormal 1-hour number and still pass overall.
I've had to do numerous glucose tests, before I was pregnant and now that I am pregnant. My tests in 2008, my 1-hour numbers were well above normal, but the rest of my numbers on my 3-hour test were great. The endocrinologist I was seeing still treated me for pre-diabetes, had me meet with a nutritionist who saw nothing wrong with my diet, and then tested me again 6 months later with no significant change in results. I lost only about 10 pounds since then, but my numbers during my first GD test at 11 weeks were SIGNIFICANTLY lower than my 2008 numbers. On one of my tests, my 1-hour number was 185 and my 2-hour was 127.
The different amounts of glucose in the glucola can have an impact on how your body reacts to it as well. And that much straight glucose in one sitting is completely unnatural to our bodies, just like sitting still for 3 hours after drinking it is! In truth, even if we're mostly sedentary after meals, we're still likely to be more active at home or work than we are in the doctor's office during a glucose test.
In your situation, I would make sure to discuss your home test results and your glucose test results together with your doctor when discussing how to approach the rest of your pregnancy. If you're not rapidly gaining weight, do your best to limit your carbs and consume more of the things that are less likely to make your blood sugar sky rocket and you're getting enough calories to support your baby, then you're doing the best you can possibly do. Starving yourself for the sake of GD obviously isn't an option. I'd also consider your first child's weight at birth since high birth weight is the biggest risk/complication of GD. If your first child wasn't a giganti-baby and you try to follow the guidelines you've created with your doctor, then a blood sugar spike at 1-hour might not be as awful for you as for other people.