Dude you have no idea then what DDOS can do!
im sure sunius knows exactly what it can do, DDOS attacks in large sometimes could take out a network device if it is degrading, but so could any electrical surge, most cases that would not happen and if it did would just usually kill a port not a whole switch or router
as well an ISP should not be holding you responsible for their hardware failing due to any type of traffic coming through.
if you can get the ip that is causing the DDOS just block it manually in your router or report the IP to your ISP.
you can also off load your website and server to a hosted server elsewhere, where they have security measure against DDOS and more bandwidth to resist them.