I don't think you're overanalyzing, no. All carbs are not the same for you (or for me, but my worst carbs may be different than yours). Apparently you're encountering not only the problems with carbs in general (raised insulin and all the downstream effects) but also food sensitivity issues.

It sounds like you should avoid grains altogether--if rice bothers you, it's not just a gluten intolerance you're dealing with but probably something in the leaky gut syndrome area. Trying some specific food rotations would be interesting. Try to stay at 50 grams eating only veggies and fruit for a few days. Then try it eating only veggies and legumes. Then try it eating only veggies and a half a potato...since you're good at noticing how you feel, you'll start seeing which carb-laden foods are also among your food sensitivities. My guess is that it isn't the carb levels so much as the particular foods that are bothering you.

Hope that helps (and hope it made sense!)