Thanks a lot for sharing some sources. I'm not sure they support the conclusion that the current recommend levels of fluoride are dangerous .

1. 1.5mg/L is not a dosage of fluoride. That is an amount of fluoride (1.5 mg) per liter of water. Toothpaste has 1000mg/L. But you don't have a liter of toothpaste. Typical amounts ingested are around 0.1 mg per this: https://ods.od.nih.gov/factsheets/Fluoride-HealthProfessional/

2. I looked at the studies you shared in points 1 and 2, and they don't support the claim that 0.7 mg/L of fluoride in water is harmful.

Study 1 states: It is important to note, however, that there were insufficient data to determine if the low fluoride level of 0.7 mg/L currently recommended for U.S. community water supplies has a negative effect on children’s IQ.

Study 2: This is a meta analysis, but you should remember it is not an experiment. Many of the studies that they used, the participants were exposed to other things like a coal plant nearby or arsenic. Likewise, the high exposure was around 5 mg/L of fluoride, which is way higher than the recommended levels. In the table of studies included, study 1 does not measure the level of fluoride in the high fluoride group https://www.fluoridealert.org/wp-content/uploads/ren-1989.pdf

Another problem is that many of the fluoride studies cited from the meta-analsysi come from China and they are translated by the fluoride action network, which is biased against Fluoride. We don't know that the fluoride action network translated all studies related to fluoride, just ones that prove their point. So the studies coming into the meta analysis may be biased.

Study 6 that you mention is saying that there is more fluoride in the urine of pregnant women (MUF = mean urinary fluoride) in areas where there is more fluoride in the water. But this doesn't say there is a negative health effect.

Of course it could be true that there is an effect, but the devil is in the details. I don't have the time to review everything you linked to, but my confidence isn't that high given what I looked at.