I dug around today and I think I've figured it out.
At least, in part...
1. ONIONS: I was eating too many carbs in the form of onions. Every time I ate tuna salad, I would eat maybe a half-cup of onions in it. Plus, I ate onion slices on the hamburgers I ate and chopped onions in the taco salad I made. I incorrectly looked at net carbs instead of whole carbs and miscalculated. 1/4 cup of onion is 2.8g NET carbs, and over 4 full carbs! I was eating about an onion a day, at around 14 carbs!!
2. RANCH DRESSING: Because I thought I was doing so well on my carb count, I also splurged on Ranch at 1 carb per tablespoon. And a few tablespoons later, plus my onion binge, and I was over 20 carbs on just those two items.
3. OLIVES: Olives have some un-displayed carb content, and I ate ten at a time. Their sodium content would have affected me as well.
4. UNMEASURED STUFF: If I'm still eating a lot of calories, it doesn't matter how low my carbs are in the first few days. I didn't measure mayo or meat portion sizes or butter. I ate more eggs than I needed. This probably didn't help.
5. DELI SLICES AND CHEESE: Okay, okay, Doc Atkins. Zero displayed carbs doesn't mean zero impact on blood sugar and ketosis induction. Gotcha. I'll quit the first and limit the second.
6. ARTIFICIAL SWEETENERS: Splenda in my Diet Rite may have little impact on my blood sugar, but it does keep me accustomed to the taste of "sugar". Maybe this makes me more prone to eat bad things.
This is all I can think of now. I'll take it into consideration when I jump into Monday morning.