Fluoride doesn't weaken the enamel except if they are still developing. Dentin has like a crystalline structure. Fluoride destroys this.

I haven't used fluoride in about 5 years and haven't had a single cavity. I go to the dentist every 6 months and he says my teeth are doing great.

Flouride can eat through cement, steel and glass. It can only be stored in plastic.

All I can say is this - last year I had a fucking terrible tooth ache. Absolutely horrendous pain. Only thing that helped was a high fluoride paste application. Now it's fine and I never lost the tooth. But normally I use a small amount of paste and only brush for a minute. The brushing is the part that ruins your enamel. Best to just let the fluoride sit in your mouth for a couple of minutes then rinse extremely thoroughly so you never swallow any.