I agree that many companies don’t know a lot of these things. I’ve contacted some companies that can’t tell me where ingredients are derived from or if the facility that processes a product also processes potatoes. It is really frustrating and because I do react to cross-contamination it means I largely avoid processed products and eating out.
With regards to reactions getting worse with each exposure, I’m fairly sure that’s a myth, at least according to most doctors (see for example Do Reactions Worsen with Each Exposure?).
I agree the glucose tablets aren’t ideal, but I consider it a calculated risk. Technically, I’ve read that maltodextrin isn’t even supposed to be capable of causing allergic reactions because it’s so highly processed that all protein (from whatever food it was derived) is fully broken down. I’ve definitely reacted to potato derivatives before, though, but only with an itchy mouth, never full anaphylaxis (I have had anaphylaxis to cross-contact with and trace amounts of actual potato, though).
So not the best choice. Unfortunately, most other candies aren’t much better because they often contain maltodextrin/dextrin and/or outright potato starch (which then means everything that company produces is probably at risk of cross-contamination). So I use them but keep my eye out for something else that’s readily-available and not too good-tasting (tried dried mangoes for a while, but they are too good-tasting…).