How many launch pads have been destroyed?

Due to spacex's starship?

Zero currently

I have to ask

This is at the second time, maybe no3 , someone has "asked" this as if its a gotcha

Where did you get that impression?

How much scrap metal, leftover fuel and mystery materials used in the heatshielding have ended up being dumped into the ocean with every test?

Gonna be honest

In the grand scheme of things , just... not much

The total empty mass(so no fuel or payload) is roughly estimated in the lower-mid to mid hundreds of tons of mostly just steel, by some definitions a vessal with such displacement may not even qualify as a ship

For the propellants? Decent chunck is just liquid oxygen, the rest is methane . By the time a landing can even be attempted most would have been used already and its just methane

Rockets useing UDMH and NTO are still in use (and have hit a village already , thats why the faa is being carefull and america builds launch complexs on the coast. Flying over land just has that inherant danger if something goes wrong, noone wants rockets falling into villages)

While i cant say much on the heatshielding i doubt it matters much , its just too little and i highly doubt its that dangerus considering noone seems to have issues with people collecting it, not only wouldnt it be inline with any other heatshield i know of haveing been used, if it was i would expect it to be plastered everywhere after flight 1

Rockets overall just dont matter

The admiral kuznetsov alone probably has a bigger impact from just staying in port (its engines are fucked due to haveing to be always on to supply it with power and it runs on goddamn mazut)

Frankly this could easly be reconstructed to support starship

All but 1 (thats also under development at a significantly earlier stage then starship, gonna guess they also will have some test flights without the expectation of landing) other rockets do 2 out of 3 of these points and dont have any plans to stop