You're going to get mixed responses from people, and there are so many kinds of keto bread. I rely on Carbonaut (Costco) and while it's been just fine for me, I have read of it not agreeing with others. If it's not spiking your GI I wouldn't worry too much about it.

Congrats, those are some good gains! One thing to remember about those strips is they measure excess ketones excreted through urine. So it may indicate that your body is producing ketones but if it throws up a negative, it doesn't mean you aren't in ketosis.

As for your (kinda) plateau, keep at it. If you're trying to lose weight, try to keep to a 20% calorie deficit. Otherwise, it could just be your body striving for homeostasis or just recalibrating itself. Keto isn't a rapid weight loss diet, so make sure you give your body space to adjust. Here's my chart, lots of plateaus.