Hello and thank you for your answer :)
"Everyone else's download is running fine" : unfortunately that's not the case at all. If you search here, on reddit or other forums, you will see that it's a very common issue with itch. Of course, you can say it's the users fault, but from my point of view, I could see that this problem is also present for my friends and on different providers.
One thing I could already see with itch, is that there is not a real helpline with people actually answering. Or to be clear, there is, but after 15 days, they never answered. Thank you again to you for answering, but an official support of itch would be appreciated : they can not just take our money and then not helping in case of issues. And I'm not talking only about this issue I'm facing now. You can see in the forums that itch are, as you sayed yourself, involved in real important money discussion with creators and some "crazy users" and don't have time for other issues. From my point of view, they should hire more people to have a real customer service, cause that's what we are : customers that payed for a game. And if I buy a game, I should be able to download it.
I can understand that you think that my internet is crappy and maybe it's an issue related to my computer, but once again, that's not the case and it seems that a lot of users in Europe are facing the same issue. Others are not and it's working well for them, but there is an issue with itch servers in certains conditions : it would be great that they at least try to see what's happening here.
So maybe that tomorrow, my games will be available again, but for how long ? It's been 15 days I can't download anything. What I see here, is that Itch has no answer for me and my games are (maybe temporarly) lost. So no, I'm not going to buy my 150+ games on another platform, but I'm clearly not going to buy any more games on Itch. Not a personnal Vendetta here, but you can understand that I must find a way to actually play my games ;) There are other providers (humble bundle, Gog, Steam and others) that are decent alternatives (and still allow me to download full speed) and that answers their customers in case of issues.
Thanks again for your time, have a nice day