Your logical fallacy is comparing moderation with homeopathy by making comparisons with foods.
Again, fluoride isn't something you can take in massive quantities without adverse side effects in the long term. You don't have to believe me.
Having specific needs due to health related issues (like in your case) isn't the norm. The norm is someone that has healthy teeth and doesn't need any kind of medication, thus they can use small amounts of toothpaste compared to what is usually shown in TV ads (pea sized vs covering the whole toothbrush in it). I said multiple times that this is true unless your dentist tells you otherwise, which is your case. Fluoride isn't good in large quantities, but when treating some other conditions you are making a compromise: normally it wouldn't be good to use too much toothpaste, but in your case it's better than having pain or discomfort. That's how most medicines work as well.
As an example I suffer from asthma. On top of lifestyle changes I have to take corticosteroids for long term management (with months long breaks in between) despite the fact that those have a huge list of severe adverse effect in the mid to long term. I do it anyway because the alternative of having asthma attacks puts my life in danger, so I'd rather risk other complications rather than death. This risk is very real as back in 2016 I spent a whole month almost suffocating to death every single day, so hell yeah I'm willing to take those risks.
My medication is the lowest concentration possible right now. There are higher concentrations available if things get more severe. The reason I'm using this and having multiple breaks, as per doctor's prescription, is that my body can get easily used to the effects and they can become less potent over time. So, I will probably have to increase dosage anyway as I get older, doesn't mean I have to shoot myself full of corticosteroids right now if I don't absolutely need to because if I do I can end up at 40 or 50 years old with no way to stop my asthma and a much more likely death by asphixiation.
These are facts, not advocating for homeopathy. That would just kill me and so many other people.