Hi,
This is why we test out our foods, so we can learn by trial and error what we can eat. Perhaps next time you dive into the Ryvita box have a look at the nutrition label for "Total carbohydrate" (ignore the "of which sugars"). They are almost 67% carbs. Reading nutrition labels on all packaged food is essential when you are first starting. Perhaps next time try one or two and see what happens. If you still spike high, then they are not for you at the moment. Oh ... and sausages are mostly cereal, so be careful with them. You can get 97% meat sausages in all supermarkets and some butchers for cooking at home.
Don't be hard on yourself. It will take time to learn which foods you can munch to your hearts content, and which you need to limit.
One tip. Sometimes it is best to test just before you go to bed, then do your morning fasting as soon as you get up. This will show you if you are getting an overnight liver dump. (Our livers produce glucose if they think we are in starvation mode as a protection, and this often happens over night. You can read up about this as Dawn Phenomenon) Our morning fastings are usually the last reading to come down.
Worry not, you are doing well.